Alternative Calendar

Who makes a calendar that has 41+ days on it? I wonder how the leap year will react to this.

Graham: Videogames are an escape. So invent your own fantastical calendar system and let the player know where your game takes place on it. With no frame of reference on when that is, or why you are telling them, they can't help but be drawn in!
Paul: Is it the past? The future? Only you will know.

— Unskippable Guide to Making Cutscenes

In Speculative Fiction, it's common to use a different calendar than the real world. This makes it clear to the reader that the story takes place either in another world, or in a version of our world so far in the future that time isn't even counted the same way. This also elegantly sidesteps the problems of Exactly Exty Years Ago.

In fantasy, a popular version of this is to measure time in "moons" instead of months. In some cases, the author will actually have twelve different names of the form "______ Moon" to replace the twelve months of the Gregorian calendar. However, there are actually somewhat more than twelve lunar months in an Earth year. Real lunisolar calendars solve that problem by adding a leap month to certain years; some purely lunar calendars (like the Islamic one) ignore the solar year altogether and just declare twelve lunar months to be a year (resulting in the lunar calendar falling behind 11 days every solar year, making the lunar months slowly rotate through the seasons over the decades, completing one full rotation every 33 years).

When an Alternative Calendar is used to measure the progress of "days", it's common for characters to use Microts as smaller, more manageable units of time. In Sci-fi settings, these calendars are frequently used across multiple worlds, becoming Standard Time Units.

If Alternative Calendar is used in Science Fiction with Earthian years, it may mean that the work takes place After the End or something else that Hit So Hard, the Calendar Felt It or that everybody have Outgrown Such Silly Superstitions and chose something significant for their reference point.

In a fantasy setting, years may be named rather than numbered. Instead of the regular cycle of year names in, for example, the Chinese calendar, these names are always entirely unique, generated by scholars through obscure, and possibly prophetic, methods. Since this is little use for actually calculating how long ago something was, they may have numbers as well.

A common Year One, Day One in science fiction is October 4, 1957—the date Sputnik was launched, thereby beginning the Space Age. The Apollo 11 landing on July 20, 1969 is also sometimes seen. Another Year One is the year Rome was founded, called 1 Ab Urbe Condita. Still another one is a future date, which may or may not be tied to a date in the Gregorian calendar.

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Examples:

Anime & Manga

As the Japanese have a history of doing this in their own history, this trope appears a lot in anime. Even when depicting cultures which are not Japanese. Some anime (particularly those meant to be set in Japan) are noted for emphasizing use of the Japanese style of years (based on the Emperors) rather than the Western straight numeric year (see the "Real Life" section). Gate Keepers used it for the year (it was set in 39 Showa—1969). The intro to Phantom Quest Corp. also interestingly used the formal dating ("Fourth Year of the Heisei Period" instead of 1993).

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• Battle Angel Alita, particularly the space colonies in Last Order, uses a calendar dating from the launch of Sputnik in 1957 AD.
• Code Geass takes place in the year 2017 a.t.b ("Ascension Throne Britannia"), counting from the establishment of the first Celtic King in the Britannian royal line, rather than the birth of Christ. The EU uses the Revolutionary Calendar, a variant of the French Republican Calendar that sets its first year to 1790, the year after the French Revolution.
• Dragon Ball takes place on a planet called Earth, but they follow an alternative calendar (the year Goku meets Bulma in the first series is given as 749, and each year is called an "Age"), the life-forms are full of Talking Animals, and it's home to the titular wish-granting Dragon Balls.
• The Familiar of Zero has a 384-day calendar divided into twelve months of four eight-day weeks. Each week in the month has its own name, in addition to the months and days of the week.
• The Girl Who Leapt Through Space is set in the year 311 O.E., or the Orbital Era, counting from when humanity began living in a space colony orbiting Earth as well as on the planet itself.
• Every Gundam series except Gundam 00 uses this; indeed, the various calendars are a common way of differentiating between Alternate Universes. Most of them identify the establishment of space colonies in orbit around Earth as the event that made the switch to a new calendar, but in several cases it's an After the End setting that uses the previous disaster as the marker.
  • As a direct result of Gundam 0079's success with the Universal Century calendar, this trope can also be found in the majority of Real Robot series produced since.
  • Based on a couple of instances where concrete dates are given in 0080 and ZZ, which reveal that January 14th 0080 fell on a Monday and the UC years that are multiples of 4 are leap years, respectively, it's possible to narrow down the year the changeover happened somewhat. Working backwards 79 years (no official timeline ever mentions a year UC 0000), we find that the calendar changed during a common year starting on a Tuesday, meaning the earliest possible candidate for UC 0001, as of this writing, would be 2019 (unlikely to say the least). Fanon tends to put it sometime between 2047^note the last official timeline Sunrise ever published that featured dates in the AD era had 2045 as the last one mentioned, but this is apparently no longer canon and 2081. Of course, this all assumes that no dates were skipped over when they changed the calendar and that leap years are still calculated the same way.
  • The Gundam Wing sequel novel Frozen Teardrop features the first Alternate Calendar within a series: while the Earth Sphere uses the AC (After Colony) calendar, Mars uses the MC (Mars Century) calendar, with years roughly double the length of Earth's. This makes it more than a little confusing as to when exactly Frozen Teardrop takes place in relation to the main series (for the record, MC 0022 corresponds to the early 220s in AC).
  • Gundam: Reconguista in G also does this, with the Regild Century replacing the Universal Century 1014 years before the series' start.
• Henkyou no Roukishi Bard Loen: The story starts in a year of 4270 by the local calendar.
• Hyper Police takes place in the "22nd Year of the Holy Century".
• Kiddy Grade takes place in "Star Century 0165". The reckoning is assumed to be the founding of the Galactic Union.
• In Legend of the Galactic Heroes, which takes place in the late 36th century AD, a new calendar (the Universal Calendar) was started when humanity left Earth and founded the Galactic Federation. The Galactic Empire replaced the Universal Calendar with a calendar counting from the year of its founding; when the Free Planets Alliance broke off, they restored it. Hence the two sides have different time reckonings.
• Library War takes place in the year 2019 CE, which is also year 31 of the fictional Seika era (see below on the Japanese era system) — Seika was one of the choices considered for the era following Shōwa in real life, but was discarded in favour of Heisei. This becomes Hilarious in Hindsight when it accidentally predicted the real 2019 as the start of the Reiwa era.
• Lyrical Nanoha uses the old and new Mid-Childan calendar, with the new one starting sometime after the end of the Ancient Belkan War, when Magitek replaced physical-based weapons as the standard due to the devastation the latter caused. Interesting in that they also use the regular Earth calendar, thanks to worldhopping. The series began in year 65 of the new Mid-Childan calendar.^note A common fan theory estimates that the New Calendar began around 1942 by Terran reckoning, so 0065 NC corresponds to 2006 CE.
• An episode of Pokémon the Series: XY hints that the Pokémon world is either a few decades out of sync with our world, or they use a different calendar. Regardless of which is true, the year in the anime is implied to be 1958 or possibly later.
• Soukaizan and Seikaizan is stated in the Mashin Hero Wataru Series manual to have different terminologies for their calendars. The date and year counts are written universally in Chinese "upper case" numerical text ^note The upper case variant is used for contemporary financal documentation as per Wikipedia’s example. The Japanese kanji system uses a form of simplified variety of the upper case., as for months, Soukaizan goes by Eastern Zodiac for their months ("Rat" equals January, and so forth), while Seikaizan goes by something along the lines of astrology, but their pattern wasn't fully elaborated.
• The Magic World of Negima! Magister Negi Magi has its own Imperial Calendar to differentiate it from the real world. The series takes place at around the year 1018 of that calendar, which is around 2003 of ours.
• Outlaw Star and Angel Links (same universe) use the TS or "Toward the Stars" calendar. Outlaw Star takes place in TS 0158. The reckoning is assumed to be the advent of interstellar travel.
• Sound of the Sky starts in the spring of 271 A.P. and ends in February the following year. While not explicitly stated, it is presumably 271 years after the huge world war ended.
• Str.A.In.: Strategic Armored Infantry has S.E., although we aren't really sure what it stands for. (According to the dub, it's Standard Era, but how canonical that is is debatable.)
• Tekkaman Blade takes place in the year 192 of the Allied Earth Calendar.
• Tiger & Bunny begins in 1977 N.C. (New Century). The only hint as to the real-world date would be the show's pilot, which makes mention of the 22nd century.
• Valvrave the Liberator which is basically Mobile Suit Gundam SEED + a little Legend of the Galactic Heroes with SPACE VAMPIRE ILLUMINATI has the True Calendar.
• Attack on Titan: Given that the rest of the world is shown to possess early 1900's technology, this is a case of an as yet unexplained calendar, with the story starting in the year 840. Quite what it's been 840 years since we haven't been told, although it's most likely related to when Marley overthrew the Eldian Empire. Nothing else beyond the year itself has been defined either, and it's also unknown if the calendar used in the walls is different to what's used outside them.
• Flower Knight Dakini uses TE (Town-Era), which represents when aiushi technology (repellent for giant bugs) was created and spread across the world, allowing for permanent towns and settlements to be made without fear of them being destroyed by the bugs.

Comic Books

• The Multiversity: In Thunderworld #1, Dr. Sivana attempts to add a new calendar day called "Sivanaday", but it only lasts eight hours.
• The world of Nikolai Dante generally uses the Gregorian Calendar, but refers to each year as 'Year of the Tsar'.

Comic Strips

• In a Calvin and Hobbes strip Calvin says that the U.S. was founded roughly around 200 B.C. - "Before Calvin".

Fan Works

• The Central Shadow Realm fanfiction series counts from a randomly-chosen point during the construction of the titular city; those living in the city admit it's arbitrary. The months and days don't have names; dates are given as "The (x) day of the (x) month". The first story, Shadow Realm: Fifteen, took place in 5178.
• The Null Verse of A Dragon in Shining Armour has its own calendar known as the Golden Calendar, which is based off the Four Holy Beasts and their Devas.
• In The Elements of Friendship, the Cult of Pi, who worshipped Discord, also used their own system of telling time — their weeks were composed of only five days (Sweetmorn, Boomtime, Pungenday, Prickle-Prickle, and Setting Orange), and their years only had five months (Chaos, Discord, Confusion, Bureaucracy, and The Aftermath), each 73 days long. And the calendar's starting point was at Discord's arrival in Equestria, which was listed as YOLD (Year of Our Lord Discord). All of this is based on the real-life Discordian calendar mentioned below.
• In From Bajor to the Black, dates by the Bajoran calendar go like "Satar 4, Seventh Era 943, Year of the Unseen Harp". The date in Earth years is given nearby.
• The Magick Knight: Guardian Seed fanfic uses the "Era of Magick" calendar, originally adopted by the "League of Nations" after the discovery of the Plants to the west and the proliferation of Adepts. Progress through the year is measured in the seasons, Winter (December-January-February), Spring (March-April-May), Summer (June-July-August) and Autumn (September-October-November). The story takes place in 70th Year of the Era of Magick.
• In Seventh Endmost Vision, Shinra declared the date of the first space launch to be the start of a new calendar, which was adopted by all territories under its control. It is listed as AS, start date pinned to the launch; notably, while it's supposed to be the Age of Space, it's clear to everyone involved that it really means the Age of Shinra, showing the company's arrogance and pride. Notably, even their own history museum notes that the Western Alliance protested the hell out of the new calendar, and the issue was presumably only settled once the War began.
• In RWBY Alternate, the calendar starts on the year that the moon is shattered, which is dubbed "Year 0". Remnant also uses the epoch "A.E." (After Empire) which refers to the fall of the old societies.
• In RWBY fic What a Wonderful World , the show takes place in Cycle 790.
• The lack of months in the Story of Seasons series is explained in Frostbitten Flower by being a personal choice of farmers. To a farmer, seasons matter more than individual months.
• The Victors Project: Post-Mockingjay Revolution Panem begins its calendar when Katniss and Peeta put the nightlock berries in their mouths. All subsequent dates are P.B. (Post Baccis- After the Berries).
  • Prior to this, the Capitol seems to have set their calendars by the end of the Dark Days Rebellion and the start of the Hunger Games.
• Oversaturated World: Group Precipitation: "Adult Fear": On a grave stone, years are noted in A.S, which is a different than expected in the rest of the stories. The Author's Note notes that as non-canon:
  And for the record, no, no one's proposed starting over when it comes to counting years. Imagine the headaches involved in converting every computer system on Earth to a new calendar.
• In RWBY fic Random Acts of Kindness , Remnant's current dating system is based on years after the Great War. The story begins in 68AW, or 68 years after the Great War.
• Ruby Pair: The Irken calendar, according to what little is shown of it in "Frosting the 13th", has all its months named after food, with the ones listed being Garnish, Frosting, and Pudding.
• Paradoxus: The diegetic calendar is counted in years after or before Domino's restoration. This means that dates are only mentioned when the characters are in the Magix dimension, never while in Azeroth. Dominis have also their own names for each month. The third chapter is the first in which this is done; by contrast, the prologue noticeably lacks it because it's meant to be a mysterious In Medias Res.

Films — Live-Action

• Every clock in Labyrinth has 13 numbers. Whether this is because Jareth gives Sarah 13 hours to solve the Labyrinth or vice versa isn't clear. In the novelization, Sarah wonders if this means that a day in the Labyrinth lasts 26 hours instead of 24.
• People in the underground city of Metropolis use decimal time, with the clocks only going up to 10. This is the time the workers spend at one shift; their days count 20 hours. The upper class has 24 hours days, and certainly don't spend half of it working.
• Played for laughs in Santa Claus Conquers the Martians:
  Chochem: What time of year is it now?
  Kimar: It is the middle of Septober.
• Perhaps to help correct the earlier Canon Discontinuity, in Star Trek (2009), the Stardate calendar they use is a cross between the old universe's Stardate system and good-old-fashioned Gregorian. Stardates from this point went XXXX.YYY, where XXXX was simply the Earth AD year and YYY was the numerical day in that year starting from 1 (New Year's) and ending in 365 (366 on leap years).
• In Waterworld, the Smokers speak of "lunars" of time. It's probably safe to assume they refer to lunar cycles. It's not clear if the length of the day or the length of the month significantly changed when the entire Earth was flooded due to the icecaps melting and all but the peaks of the Himalayas sinking under water.

Literature

• The Animorphs prequel ''The Hork-Bajir Chronicles" gives Earth dates (the late 60s), Andalite dates (a year in the 8000s with decimals attached), Hork-Bajir dates (simply a reference to the current season) and Yeerk dates (a reference to generational cycles).
• The "Common Era" in Alexei Panshin's Anthony Villiers novels apparently is reckoned from the launching of Sputnik I in 1957.
• The Ardrana series of freely available online short stories feature the Lanad Calendar. There are thirty days in a month and 361 days in a year, leaving one hanging day, Day of Change, a holiday that doesn't fit into any of those months. The Day of Change is considered both the end of one year and the beginning of the next at the same time. The years count from the founding of the "Third Civilization", details of which have been lost to time.
• Isaac Asimov:
  • "Blind Alley": The memos in this story are dated from 12/977 G.E. until 1/978 G.E., making the system day/year since the founding of the Galactic Empire and taking place in under a year.
  • Foundation:
    • While the empire that based their capital on Trantor is ascendant, the calendar used across the galaxy is the Galactic Era. Year 1 of the Galactic Era begins over 12,000 years before any of the Foundation stories, and thousands of years in our future.
    • While the empire that based their capital on Terminus is ascendant, they name their calendar Foundation Era. Year 1 of the Foundation Era begins when they establish the Encyclopedia Foundation on Terminus in 12,069 GE.
    • Foundation's Fear: (Subverted Trope) As noted in the Afterword, how year 1 of the Galactic Era fits in with Anno Domini can be difficult to determine, as Pebble in the Sky establishes hyperspace travel has been around for hundreds of thousands of years, Foundation (1951) establishes atomic power has only existed for fifty thousand years, and Prelude to Foundation establishes R. Daneel as being twenty thousand years old. Since these conflicting dates were impossible to reconcile, Benford chose to simply rename A.D. to G.E., and treat the Trantorian calendar as a continuation of Earth's Western calendar. However, it also renames the months, such as Octdent (October) and Marlass (March).
  • "In a Good Cause—": This story gives three dates, counted in years since the first atomic explosion. These three dates are the times Altmayer was sent to jail for his beliefs: June 17, 2755; September 5, 2788; December 21, 2800.
  • "The Last Trump": The End of the World as We Know It is scheduled to take place the first minute of 1957, but Etheriel uses the existence of alternative dating methods to argue with God into allowing Earth to continue until everyone agrees the year is 1957. Satan immediately gets to work on supporting proposals for years to be measured from the Atomic Era.
  • "Living Space": The protagonists use the Anno Domini calendar (possibly with minor changes), but when Alec Mishnoff asks the German-speaking builders he's encountered what year they think it is, he finds that they're measuring time since Hitler's rise to power (Nach Hitler).
  • Pebble in the Sky: Every planet in the galaxy now uses the Galactic Era calendar, which starts from the coronation of Frankenn the First, 827 years before the main setting of the work. (The book started in the 1950s, then Time Travel moved the setting, some fifty thousand years or more into the future.)
    "It's 827 years since the foundation of the Galactic Empire; 827 years since the coronation of Frankenn the First.
• Works in the Bas-Lag Cycle, including Perdido Street Station, The Scar, and Iron Council, use rather bold-faced names for the days, such as Skullday, Chainday, and Fishday. And this is only for the city of New Crobuzon, alone. In the floating city Armada, they have completely different names for months and days of the week.
• David Eddings' The Belgariad uses the Alorn Calendar, which measures time in years since the cracking of the world. The Alorn calendar also measures their year in seasons instead of months. Additional calendars used by other nations are occasionally mentioned throughout the series, with one notable one being the Tolnedran Calendar, which marks the Xth Year of the reign of the Yth Emperor of the Zth Dynasty of such and such a house.
• Brave New World reckons its time from the completion of Henry Ford's first Model T^note AD 1908 ("in the year of our Ford"), as part of its satire of the post-Industrial Revolution world. Ironic, considering that Ford himself said "History is bunk," and is quoted as such in the book.
• Edgar Rice Burroughs:
  • In Pellucidar, the immobility of the central sun prevents any sort of celestial timekeeping, leading the protagonists to proclaim (unconvincingly) that there is "no such thing as time" at the Earth's core. In fact, time in Pellucidar passes more swiftly for you when you're exerting yourself more. At one point, the hero and his friend were separated and the hero had several weeks worth of adventures: fighting, running, lots of hard work. His friend merely strolled back to their lodgings, so only about an hour passed for him. It's a pity the "I'm not making this up" category has been disabled, because this nonsense deserves it.
  • In John Carter of Mars, it gets rather more rational treatment: he believes Dejah Thoris has died in The Gods of Mars because it has been a year — but he has forgotten he's on Mars. The Martians have their own methods of counting time based around the "ord" (Martian year), analysed in detail (along with their inconsistencies) in this article.
• The Cold Moons: Badgers do sometimes use standard terms for seasons, but they usually call spring "the birth time", summer "the warm time", autumn "the time of falling leaves", and winter "the time of cold moons" ("the cold time"/"cold times" for short). Days are counted in suns (for example, "forty suns") and a month is "a complete life of the moon" (or just "a moon").
• Cradle Series:
  • Word of God is that every culture, and in some cases every region, uses an entirely different calendar. Apparently, the heroes pass through at least four different calendar systems in the first few books. This mostly doesn't show up in the text, except for when Lindon is surprised that the Empire counts him as slightly older than his own culture would—his culture counts age from the new year (which is a real phenomenon in some Asian cultures), while the Empire uses Life artists to measure from his actual birth.
  • In Dreadgod, when an ancient dragon comes out of a Time Stands Still field, he demands to know What Year Is It? in "the Obsidian Calendar." Orthos awkwardly says he's never heard of that calendar.
• In Stephen King's The Dark Tower, Roland's world uses different names for the months.
• In Vernor Vinge's A Deepness in the Sky, interstellar traders have done away with not just years and months, but also with days, hours and minutes. All timespans are measured in (appropriate powers-of-thousands of) seconds, with dates simply being the number of seconds since the UNIX epoch (with some unspecified but explicitly mentioned relativistic frame corrections) — though in-universe it is most commonly thought that the zero-second was at the first moon landing. Settled planets all have their own calendars. One way the traders know they have stayed too long is when they start using the locals' calendar.
• Joan D. Vinge (who Vernor Vinge was married to at the time) used the device of measuring all time spans in large multiples of seconds in her Heaven Chronicles, published 20 years earlier. Here times are given relative to the arrival of the starship "Ranger" in the Heaven planetary system. Word of God, or at least of Joan Vinge, is that the Heaven Chronicles occur in the same Zones of Thought setting Vernor Vinge used for his later stories.
• In Jack Vance's The Demon Princes, the year zero corresponds to the year 2000 A.D. Therefore the first book taking place in 1524 means that it is really 3524 A.D.
  • The fact that the new calendar began in 2000 A.D. is only given in a footnote.
  • A foot note in the 4th book, written after Apollo XI, retcons the epoch from 2000 A.D. to 1969 A.D.
• Brian Caswell's Deucalion uses a metric time system of years AS (After Settlement), dating from first landfall on planet Deucalion (Earth still uses conventional time).
• Discworld naturally uses a different calendar, because it's flat and seasons work differently there. Terry Pratchett eventually codified it so that each year was 400 days long, divided into twelve months with four weeks and one with two weeks, with each week having eight days (all with the same name as Earth's, plus "Octeday"). The months are named kind of like ours: Ick, Offle, February, March, April, May, June, Grune, August, Spune, Sektober, Ember, and December. The calendar year begins on the onset of winter on Hogswatch, the Discworld equivalent of Christmas. However, wizards and astronomers, who care about this sort of thing, think of each year as 800 days long, to take into account the way Discworld's sun works, which makes every season happen twice a year; to them, every other Hogswatch is a different holiday called "Crueltide". That said, the system is cobbled together from different mentions of dates in different books, some of which were based on the Earth calendar (like "1784") and some of which were made up (like the "Year of the Diffident Squid"); continuity errors are accounted for by claiming that each part of the Disc has its own calendar system (Ankh-Morpork has restarted its calendar several times in its history). Wyrd Sisters mentions several different calendars used by different countries and kingdoms, including one used by the Theocracy of Muntab, which counts down instead of up — no one's sure why, but most agree it's not a good idea to be around when it hits zero.
• Steven Brust's Dragaera novels use "in the Xth year of the reign of Empress Zerika" (or whoever's on the throne). For more formal dating, they also have a more complicated system of Great Cycles, Cycles, Reigns, Phases, Turns, and Years; each (save "reign") is exactly 17 of the next stage down, and the entire calendar starts with the formation of the empire. Weeks are five days.
• The Dragonlance series. There are seven days each week and twelve months each year. But each day and month have eight different names, each from a different culture. The titles of the Chronicles trilogy, in the Gregorian calendar instead of elven are: Dragons of October, Dragons of January, and Dragons of March. The War of the Lance lasts less than a full year. And now you know.
• The Draka: The Draka introduce a new calendar after winning the Final War.
• Frank Herbert's Dune dates events from the establishment of the Spacing Guild's monopoly on space travel; the original novel Dune begins in the year 10,191 A.G. In addition, in God-Emperor of Dune, it's implied that the (3000-year) reign of the titular God Emperor Leto II has in effect become a calendar. The prequels written by his son and Kevin J. Anderson avoid going into the pre-Guild calendar by having the events simply be compiled and retold by Irulan, so naturally she uses the same calendar, with the dates being B.G. (Before Guild).
• The timeline of The Empirium Trilogy is split between three eras: the First Age, the Second Age, and the Third Age. Rielle's story takes place during the Second and Eliana's during the Third.
• In Claire Winger Harris' short story "The Fate of the Poseidonia", Earth's calendar has been simplified to have 13 months of 28 days, plus a New Year's Day that's separate from any month.
• Human scholars in the Garrett, P.I. series use the dwarven dating system, because humans' own calendars tend to change too often as monarchs re-start their kingdoms' year count from their own births or coronations.
• In The General Series, dates on the planet Bellevue are calculated from "the Fall" of the interstellar Federation to which the planet once belonged.
• The nations of Euterpe in Teresa Edgerton's Goblin Moon use a calendar of nine forty-day "seasons", rather than months. The actual solar year is a bit longer than that, so celebratory "intercalary days" round it out every three seasons.
• On Gor each city-state has its own calendar, counting Year X of City Administrator Y's reign or some other locally-important event. To standardize, most city-states also count in years C.A. - Contasta Ar, "from the founding of Ar", the largest city-state. Actual book quote:
  Chronology is the despair of scholars on Gor.
• Guardians of the Flame: On the Other Side, the calendar uses "tendays" instead of months and weeks, as the planet has no moon.
• Honor Harrington:
  • The books count from 2103 AD (Gregorian) as 1 PD (post-Diaspora), the year that the first generation ship left Earth. The events of the books take place in the early 20th century PD (41st century AD). Planets set their years as "Year X AL (After Landing)", with days and months set as appropriate to planetary conditions. This means that a given planet will retain at least two calendars: the "Standard" (PD) year and the "Local" (AL) year. The ones that are part of a multi-planet polity will track the capitol planet's year AL. Yay for computers.
  • The religiously-founded planet Grayson averts this, using the Gregorian calendar even though it doesn't even remotely track with local conditions. For added confusion, the Graysons use the initials A.D. to mean Anno Domini, whereas in the rest of the universe A.D. stands for Ante Diaspora.
  • The Kingdom of Manticore itself starts off with 5: Terran, Manticoran (the official one for the kingdom), Gryphon, Sphinxian (the latter two for their own seasons and days), and Medusan. Each additional planet that's added to the Kingdom adds another one.
  • Nearly every mention of any amount of local years will be accompanied by "XX in T Years" (i.e. Terran years) to make sure we Earthlings have some frame of reference. Justified in this case: because of the kingdom's multiplicity of calendars, you'd expect to see them using a common frame of reference. Those people who have to deal with multiple planets and other nations (with their own calendar systems) are probably routinely doing conversions in their head automatically. You can see the same thing with people who use both metric and imperial measurements.
  • Since Manticore is a merchant empire, it's extremely common for Manticorans to move to and from different planets, so local calendars are usually of little use to those new nomads. The series being Military Science Fiction, it concentrates mainly on exactly this type of character, so the series generally dropped references to the local calendars and is now written mostly around the P.D. calendar.
• The Hour Before Morning has years reckoned up from the beginning of the dominant empire — more than two thousand of them, and an uncertain period between that and the time Earth passed into legend.
• Sacred and Terrible Air: Like with Disco Elysium, zigzagged. Centuries aren't numbered, but individual years within a century are — the story is set in '52 and '72 respectively. The days of the week and months of the year do line up with the Gregorian calendar however.
• Erin Hunter:
  • Bears in Seeker Bears measure months in moons. Bears use different terms for the seasons depending on the species: Polar bears have Snow-Sky, Snow-Melt, and Burn-Sky. Black bears and grizzly bears share Cold-Earth, Fish-Leap, and Leaf-Time.
  • In Survivor Dogs, dogs and wolves count months in moons. So, one month would be "one full journey of the Moon-Dog". A day is "one Sun-Dog journey". The seasons are Tree Flower, Long Light, Red Leaf, and Ice Wind.
  • Warrior Cats uses the "moons" type, having the cat characters measure things in lunar cycles. They also have different names for the seasons. (Leaf-bare for Winter, Newleaf for Spring, Greenleaf for Summer, and Leaf-fall for Autumn/Fall.)
• David Foster Wallace's Infinite Jest is set in a not-so-distant version of America after the adoption of a calendar system that names each year after a corporate sponsor. Most of the book's plot takes place during the Year of the Depends Adult Undergarment. It's that kind of book.
• Austin Tappan Wright devised a fictional calendar for Islandia, which is explained in more detail in Basil Davenport's treatise on Islandian history. When Islandians found out about the Gregorian calendar, they liked the idea, but adapted the month names so they would have the right seasonal connotations for the SOUTHERN hemisphere. Thus, "Octen" and "Noven" are roughly the northern April and May.
• In The Kingkiller Chronicle, a week is called a "span" and has eleven days. It's unknown how many spans there are to a month, nor months to a year.
• Ursula K. Le Guin's works:
  • The Hainish 'verse has scores of different calendars:
    • In The Left Hand of Darkness, Gethenians count years backward and forward, with the current year always being year one. The more exact dates are determined by their relation to some historical events.
    • In Planet of Exile, Werel has a 400 days' lunar cycle and a solar cycle of 60 moonphases. Year, lifetime, what difference?
    • In Rocannon's World, Rokanan has years twice the length of an earth year (or, rather, the standard year used by the League of Worlds). Some regions use two twelve-month (or however many they have) cycles to make up a full year.
  • Curiously, the fantasy book Gifts uses the Gregorian month names, but this might be a Translation Convention, and it's not clear if it's meant to take place on an alternate Earth or another planet.
  • The Kesh People in Always Coming Home don’t have a calendar in the usual sense, although they keep track of certain multi-year cycles for the sake of things like wine age.
• The Machineries of Empire features Applied Phlebotinum that depends, among other things, on lots of people following the same calendar and believing the same things. Entire wars are fought over preventing (or creating) "calendrical rot."
• The Maze Runner: According to the fifth book, the series is set between the 210s and 230s. Yet the fourth book namedrops the "War of 2020". It is implied that the War was a seminal event that caused everyone to agree to reset the year to zero, and the series is thus set over two centuries in the future.
• A Memoir by Lady Trent: Isabella's world, though less advanced than ours, is in its sixth millennium (the calendar system being based off the Jewish calendar system). The names of the months and days of the week are also different from ours. See the wiki for a more detailed explanation.
• The Neanderthal Parallax: The Neanderthals lack agriculture and religion, therefore they use a calendar that isn't influenced by them, following the actual lunar (for months) or solar (years) cycles. Further they measure things by "tenmonths" (295.32 days), "hundredmonths" (8.085 sidereal years) "thousandmonths" (80.853 years) and divide the month by the moon's phases for controlling population growth (with males separate from females during ovulation most times). Decades are still used to denote generations though.
• The various chapters of Out of the Dark provide the date in both the Gregorian and the galactic standard calendar. The epilogue introduces a third calendar, replacing the Hegemony's calendar with the notation "Year 1 of the Terran Empire".
• H. Beam Piper's Terro-Human future history (e.g. Little Fuzzy, Uller Uprising) uses Atomic Era dating, starting the year zero A.E. at 2 December 1942 by the C.E. calendar (the date of the first self-sustaining nuclear chain reaction). Characters occasionally speak of Nth Century Pre-Atomic dates to refer to dates before that time.
• Red Queen: Norta uses the so-called "New Era" calendar, whose reckoning began with the kingdom's establishment by Tiberias Calore I.
• The Reflections of Eterna series is set in a Constructed World that uses a calendar based on 400 years-long Ages, each associated with one of the four elements (four being the Arc Number of the series): the Age of the Waves follows the Age of the Lightning, followed by the Age of the Rocks, the Age of the Wind, and then Lightning again, in a cycle. Historically, each End of an Age, called "Fissure" in-universe, has been accompanied by massive political and social upheavals: for instance, the last time it occurred (the Rocks succeeded the Waves), the millenia-old empire of Taligoia was taken over and rebuilt from scratch into the kingdom of Talig by a charismatic usurper. The series itself opens in the year 399 of the Age of the Rocks, soon to be replaced by the Wind—and there are Signs of the End Times all over the place this time around.
• The Reynard Cycle: Though no dates are ever mentioned (leading to much fan speculation about exactly when and where the story is taking place), the months of the year have names like Pearlmonth, Bloodmonth, Reaping, etc.
• The titular planet Safehold has a ten month year with weeks lasting five days and an additional hour tacked on to each day, called Langhorne's Watch, to account for the 25 hour length day compared to Old Terra. Years are a bit trickier. The Safeholdian calendar initially tracked years from the Day of Creation, but less then a century later came the War of the Fallen, which was a Hit So Hard, the Calendar Felt It, and the years started over from zero. This actually causes the protagonists problems after they learn about the impending return of one or more of the God Guise archangels in a thousand years time, because they don't know what starting point the thousand years is counting from.
• In Melanie Rawn's Saga of the Exiles, the year is divided into 36 10-day weeks, each with a name and a patron saint, plus a handful of feast days for a total of 366 days. This replaced a system where every day had its own patron saint. Needless to say, this particular setting has a lot of saints.
• Sholan Alliance: Justified in that Shola's year is several days longer than Earth's 8766 hour orbit.
• A Song of Ice and Fire is set in the second to third century after Aegon's Landing. The seasons are random in length, but are much longer than the years, making it uncertain what a "year" actually means (probably related to a complete rotation of the sun, our own calendar is measured as such, rather than the passing of seasons). Word of God clarifies that, like on Earth, there's 12 moon turns in a year.
  • The Princess and the Queen, or, The Blacks and the Greens eventually reveals how Westerosi count months. Months don't appear to be named, but rather called "first moon", "second moon", etc. Months start on the new moon, "when the moon turns", so it seems to be a primarily lunar calendar.
  • The World of Ice & Fire clarifies an in-universe misconception — namely, that the Westerosi calendar doesn't actually begin at Aegon's Landing and the start of his Conquest, but the date when he was officially crowned as King of Westeros at the end of the Conquest, which was a couple of years later.
• In Star Trek: Department of Temporal Investigations, alongside multiple human calendars including Christian, Islamic, Hindu and Mayan examples, the chapter headings include dating systems from many Star Trek cultures, including Vulcan, Andorian, Cardassian, Klingon, Deltan, Tandaran and Risian. Most of these alien calendars have been plotted out in full by the author in his annotations. Other Star Trek Novel 'Verse books have given dates in mostly consistent Klingon, Vulcan, Romulan and Andorian calendars, but this is probably the first time the entire calendar has been plotted for so many races.
• Star Wars Legends counts dates as "BBY" and "ABY", Before and After the Battle of Yavin, where the first Death Star was destroyed. Mention is occasionally made of the old Imperial Calendar that was used by the Empire, which marked as the zero date the founding of Palpatine's New Era (Empire Day, 19BBY). At one point Luke, doing some historical research, expresses exasperation at each new regime feeling the need to implement a new calendar, which makes pinning down dates more difficult. As for the months, originally the setting used a 10-month calendar where each month had 35 days, with three 5-day festival weeks and three other holidays added to give 368 days. However, in a few later works a 12-month system was retconned in. Some works have a Galactic Standard Calendar based on Coruscant's (the capital of the Republic and later Empire), which had multiple variants, and may account for the discrepancies. Some planets and systems also use their own calendars-Wookiepedia lists about ten or so.
• The Stormlight Archive: Roshar has a calendar based around the highstorms, since seasons are random and only last a couple weeks at a time. Each year is five hundred days, with the end of the year marked with "the Weeping", two weeks of constant light rainfall and no highstorms except for one right in the middle — though every other year is a Light Year, with no highstorm in the middle of it. Together, each pair of years creates the thousand day cycle of storms which influences everything. This does mean that the characters are older than their stated ages. However, Rosharan days are also shorter than Earth days, so in the end a single Rosharan year is only ten percent longer than an Earth one.
• Swastika Night: Not only are years counted based on Hitler, but the months have also been renamed to honour high-ranking Nazis (though the only one we see is "Himmler", which was once June).
• Tailchaser's Song: Instead of evening, morning, afternoon, etc cats have different Hours: "(Hour of) Stretching Sun", "(Hour of) Unfolding Dark", "(Hour of) Deepest Quiet", "(Hour of) Final Dancing", etc. Summer is referred to "Hour of the Smaller Shadows", but other seasons aren't named. A month is measured in moons and is referred to as an "Eye" (as in Meercat Allmother's, their God's, eye, which they believe the moon to be). The moon cycles are referred to as the eye "shutting" and "opening".
• Tasakeru: The in-universe calendar was intentionally designed to be roughly convertible to Earth-calendar format.
• Tolkien's Legendarium (The Lord of the Rings etc) has several calendar systems for the different peoples. Used most commonly in LotR, the Hobbits' Shire Reckoning uses a reformed calendar in which the week and the year are synchronized, and hides it behind a Translation Convention. The Dwarves appear to use a different calendar, leading to such things as Gandalf in The Hobbit saying to Thorin "on the twenty-first of April, a hundred years ago last Thursday" when, in the Shire Reckoning, the twenty-first of April always falls on a Friday. Not only did the Hobbits and Dwarves have their own calendars, but so did Elves and Númenorean/Gondorean Men as well. The Númenorean calendar is based on the French Republican Calendar with names of the months translated into Elvish.
• The Towers Of February: In the alternate world Tim winds up in, the months have the same names as in our world, but they all are 30 days long, and there are 5 unnamed days at the end of the year. The first clue he gets that he's in a strange place, is that when he asks someone "What day is it today?", they answer "30 February".
• The glossary of Robert Jordan's The Wheel of Time books states that the world is on the third or fourth calendar since Rand, in a previous life, broke the world. Ten-day weeks also appear at some point, though the first few books used seven-day weeks. There are also months, but most people ignore these and just go by seasons.
• When the Blue Shift Comes by Robert Silverberg is set in "Year 777 of Cycle 888 of the 1,111th Encompassment of the Ninth Mandala" ... a fact which the Lemony Narrator cheerfully points out conveys absolutely nothing to the reader beyond being so far in the future that all our calendars have been forgotten.
• The Witcherworld knows at least two calendars, human and elven. The world's actual year length appears to be used by the human calendar, while elven year's length appears to be some two thirds of it. Both share equinoxes and solstices as points of reference.
• The Vorkosigan Saga has an alternative fiscal calendar that changes with each Emperor. Thanks to the fact that the Counts officially give the Emperor a "birthday present" of a substantial amount of money instead of doing something as explicitly subservient as paying taxes (which happens to be in the amount that their district would have owed in taxes if they paid taxes), the Barrayaran tax calendar is centered around the Emperor's birthday. This also means that in transition years, the Empire can have anywhere from zero to two tax days in it, depending on the order of the old emperor's birthday, the new emperor's birthday, and the day the old emperor died.
• In Raymond E. Feist's The Riftwar Cycle, the Midkemian calendar:
  • Has a year that's 200 days long and divided into 11 months, mostly all of different lengths.
  • Starts on Midsummer's Day, the only day in the inter-year buffer month of 'Banapis.'
  • Has one other in-year one-day buffer month in 'Mid-Winter.'
  • Six of the other eleven months are between ten and eighteen days long; the remaining three run for between 37 and 45 days.

Live-Action TV

• Andromeda has one calendar system but several reckonings. The base calendar is the Commonwealth Year (CY). Its reckoning is the founding of the Vedran Empire (the precursor to the Systems Commonwealth), nearly 10,000 years ago, when it was known as the Coronation Year. Dates before the founding are described as Before the Imperial Era (BIE). There is a point of correlation: the English translation of Thus Spake Zarathustra (AD 1891 = CY 6811), and it has been stated by Word of God that Vedran years were roughly equal to those on Earth. Then you have the most recent calendar, AFC (After the Fall of the Commonwealth), which has only run for about 300 years (AFC 1 = CY 9787).
• Though the original calendar system is not explained, Battlestar Galactica (2003) makes reference to a (new) calendar system after the exodus from New Caprica. After passing a guilty sentence on a Cylon collaborator, the date is stated as the "third day of the Second Exodus."
• Caprica introduces a twelve-month calendar using the same names as the Roman calendar: Ianuarius, Februarius, Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November and December. The Roman months Quintilis and Sextilis were renamed after Julius Caesar (July) and Augustus Caesar (August) respectively.
• Carnival Row: By The Burgue's calendar it's now the seventh century, according to Imogen's comment. There are also days of the week that are different, like "Wrensday," and different months too.
• Doctor Who: In "The End of the World", the Doctor claims that the year to which they've traveled is "5.5/apple/26, five billion years in your future".
• Killjoys: The year is apparently "1062", without any explanation as yet of what the starting point was.
• The Lord of the Rings: The Rings of Power: For some reason, Waldreg uses the word, Trewsday, the Hobbitish word for Tuesday, implying that an alternative calendar is used, coming from a Hobbitish dialect of the Westron, that has yet to exist.
• The Red Dwarf episode Better Than Life had a newsreader announce the news for Friday the 27th of Geldof.
• Star Trek's famous stardates, though these are much more complex than most. They also use straight-up AD/BC.
  • The writers of Star Trek: The Original Series made up stardates as they went along without any sort of linear progression or continuity. Early fans who tried to use them to reconcile episodes' production order and air date order tended to end up as inmates at Tantalus Colony. When an interviewer asked James Doohan how stardates worked, Doohan replied (paraphrasing), "Sorry, even Scotty couldn't figure that out." The writers guide for the series attempts to Hand Wave these discrepancies by claiming "Stardates are a mathematical formula which varies depending on location in the galaxy, velocity of travel, and other factors, can vary widely from episode to episode."
  • For the three "middle children" of the series (Star Trek: The Next Generation, Deep Space Nine, and Voyager), the stardates have some coherency. They range from the 41000s for TNG's first season to the 54000s for the last season of Voyager. Originally, the 4 stood for the 24th century, the 1 stood for the first season, and the last three numbers were given out linearly to the episodes of a season, with the digit after the period representing a fraction of days. Deep Space Nine started during TNG's run and used similar stardates, so the 4 had to lose its "24th century" meaning and the second number lost its season meaning, leaving a seemingly coherent in-universe system: a thousand stardate units equal a year. Voyager continued this, and so did the TNG movies. While this may seem like it makes sense, there are countless contradictions, errors, and inconsistencies.
  • Notably, this system would place Stardate 0.0 at 1st January 2323 AD... some thirty years after the events of Star Trek VI. Which isn't necessarily a problem, if the Federation changed the Stardate system at some point along the way, like what we know they did with the warp speed scale.
  • The Deep Space Nine episode "Soldiers of the Empire" reveals that Klingons use a stardate system of their own (day in the year of Kahless). Kahless was the founding figure of their civilization, so it makes perfect sense to them.
  • Star Trek: Discovery uses a similar system to the original series — that is, four digits plus a decimal place and not much consistency.
• The video compilation "VIDEO VICTIM" includes a skit where Japanese comedy duo Rahmens introduces us to the new world calendar.

Music

• Year Zero by Nine Inch Nails. The story takes place in the United States in the year 2022; or "Year 0" according to the American government, being the year that America was reborn.

Podcasts

• In The Hidden Almanac, most dates are given in what appears to be the Gregorian calendar, but events in Echo Harbor are described as taking place in years with names like "Year of the Dripping Moon" instead of numbers.

Radio

• The Burkiss Way's parody of Nineteen Eighty-Four begins on Scargillday 14 Vanessagust^note Referencing militant miners' union boss Arthur Scargill and left-wing actress/activist Vanessa Redgrave.

Tabletop Games

• Critical Role: Tal'Dorei Campaign Setting includes the calendar used in the Critical Role stream the book is based on. The calendar has eleven months in a 368 day year, with various months spanning 29 or 32 days instead of 30 or 31. The book mentions that the names they use for months and days are the elven names, which are apparently commonly used throughout Tal'Dorei, but regional variants do exist.
• The Dark Eye has several calendar systems. The most common (at least in the Middlerealm) is one that uses a year of 365 days with 12 months of 30 days each, named after the Twelvegods (Praios, Rondra, Efferd, Travia, Boron, Hesinde, Firun, Tsa, Phex, Peraine, Ingerimm and Rahja). The five days after Rahja are called "Nameless Days" and are dedicated to the Nameless God (you better stay at home during those!). The year 0 can be either the fall of the city Bosparan, the year Emperor Hal (or Reto) ascended to the throne, etc. And that's only for those believing in the Twelvegods.
  • There is only one god and His name is Rastullah.
  • Everybody (besides the disciples of Rastullah above) uses the calendar of the Middlerealm, just with other names for the months. And even the disciples of the Onegod observe the Nameless Days.
  • And that's just the human side of things. Orcs count years of 240 months, 28 days each, Achaz (lizardmen) have weeks of five days and months of 33 days, and so on.
• The biggest Dungeons & Dragons campaign settings include some form of alternate calendar. This converter contains most of them.
  • Greyhawk: The calendar is one of the most well known, even having a Wikipedia article covering it. A year on Oerth is precisely 364 days long with no leap years, due to the "Greyspace" solar system actually being a geocentric system. The calendar year is split into twelve months of 28-days each and four 7-day festivals, which are every three months. Due to this, each weekday always falls on the same day every year. The months follow the lunar cycle of Luna, with the festival weeks following the lunar cycle of Celene.
  • Forgotten Realms: Faerün was hit with it rather hard. The main calendar is Dale Reckoning (DR), aka Freeman's Reckoning (FR). Present Reckoning (PR) is zeroed at the Time of Troubles. The Roll of Years names years (i.e. "Year of Rogue Dragons") according to the prophecies of the seers Augathra and later Alaundo covering -422 DR to 2163 DR — which at least helps to stitch local numerical calendars together. There are even different versions of this, where the orcs started out the year in a blaze of conquest and by the end of the year had been kicked back into their holes once they'd pissed enough people off. They call that "The Year We Went Too Far". The Forgotten Realms also uses a ten day week (called, appropriately enough, a tenday) and several feast days, holidays, and other events that vary from nation to nation throughout the year.
  • Eberron: A year consists of twelve months (each named after one of the twelve moons) and a week of seven days, seeming like they just came up with with fancy new names for the months and and days to seem exotic, however the months are only 28 days each, making all characters a couple of years younger in real time than they seem. Interestingly (or not, depending) there was originally one more moon, implying before the appropriate cataclysm the year and lunar cycle used to be much closer to Earth's.
  • Mystara: A year is 336 days long, allowing for a handy calendar of twelve 28-day months. There is no distinction between the lunar and solar calendars, as new or full moons always fall on the same dates in each year. Each country has its own names for the 12 months; the chief exception is that of the shadow elves, whose year consists of 24-day months, each named for one of their religion's 14 Verses. (Being subterranean, these elves don't need to synch their calendar with celestial events, and keep track of dates only to schedule their religious ceremonies.) Inside Mystara, the Hollow World's stationary inner sun doesn't provide for conventional day/night or seasonal cycles. Rather, dates are tracked by the orbits of the major flying continents.
  • Dark Sun: On Athas, the calendar system is a merchant's calendar that is used by all of the known Merchant Houses to help with trade, which is based primarily on the orbits of the two moons, Ral (11-years to return to the same orbit) and Guthay (7-years to return to the same orbit) which each year for each moon designates a certain word used to define the year (Tyr's Free Year 1 is the 4th year for Ral, designated "Priest", while it is the 5th year for Guthay, designated "Defiance", so it is the Year of the Priest's Defiance). The calendar year is typically broken into 15 months comprised of 5 weeks each 6 days long (30-day months). A rather complex calendar system overall. The actual year numbering is either based on the King's Ages (older system), or since Tyr's revolt (Free Years).
  • Dragonlance: People started numbering up from zero after the Cataclysm, so the abbreviation was A.C., anything before the Cataclysm was labeled P.C., and after what is sometimes called the Second Cataclysm in Dragons of Summer Flame, S.C. was used for a while, but was later dropped in official supplements and novels, going back to using A.C.
  • Ravenloft: Subverted. The calendar works like Earth's, despite the setting's having been cobbled together from bits and pieces stolen/copied from other worlds. The Barovian calendar predominates for the numbering of years, while the names of months would seem to have been imported from Mordent.
  • Planescape: There are no real seasons, as each plane has different physical laws. Weeks have seven days, and years have 12 months, but their names reflect the calendar of whoever is keeping track. In Sigil, years are often measured by the year an influential Factol has held his position, usually the Factol of the Guvners (seeing as they're in charge of keeping the records.)
  • Exandria has a 328-day calendar year divided into eleven months, which themselves vary in length anywhere from 27 to 32 days. This leads to a shorter year than Earth's, but the new year begins in the middle of winter, as Earth's does. The different months and days of the week vary somewhat from culture to culture, but most have adopted the Elvish names for them. The years are numbered Post-Divergence, the Divergence being when the gods sealed themselves away behind the Divine Gate and ceased to interact directly with the mortal world, bringing it into its fourth age. The second campaign of Critical Role is set in 835 PD.
• Exalted uses a dating system starting with the founding of the (second) Realm, and has a rather different calendar inside each year also. The year is divided into 15 months (ascending, resplendent, and descending Element, where Element is one of Air, Earth, Fire, Water, Wood (not in that order)), plus five days of Calibration that are not actually part of the calendar, when spirits are at their strongest and the gods are all partying.
  • The various different regimes use different calendars, many of which will be in use at the same time in different places. The nominal "start of game" year would therefore be Realm Year 768; 4878 Dawn of Autochthonia; Year 4999 of Our Everlasting Glory and the Year of the Mouse in the Bronze Era of the 11th Epoch the Dragon-Blooded Shogunate.
  • Being Exalted, it also has an extremely alternative calendar — the Calendar of Setesh, which not only tracks time in the Underworld, it actually cements the concept of time passing in a linear fashion down there.
  • An interesting detail is that despite having 425 days, each of 25 hours, in the year, a sixteen-year-old in Creation is functionally equivalent to a sixteen-year-old on Earth.
• Iron Kingdoms: The setting uses a calendar where seven days make a week, four weeks make a month, and there are thirteen months per year. Furthermore, the days are not named, but the weeks are, and the whole thing is based around the cycles of the planet's three moons. Every three years, all three moons are new on the same night, which makes an extra day on the calendar. This 'Leap Day' is celebrated in a festival called The Longest Night.
• Magic: The Gathering: The world of Dominaria has an undefined calendar within the year, although years are given in several different scales. A nation famed for its education and archaeologists is even referenced in the name of the most well-known calendar — Argivian Reckoning (AR), which places Year 1 on the year Urza and Mishra, leaders of the two sides of the Brothers' War, were born.
• Paranoia: The days of the week are as follows: Oneday, Twosday, Threeday, Fourday, Fiveday, Sixday, and Mandatory Inspection Day. The year is 214. See, the Computer decided that 214 makes things sound nicely established but not too old, so the year is always 214.
• Rifts: Some places use the Gregorian Calendar, but, in North America, the Post-Apocalypse (P.A.) calendar is used. It was established by the Coalition States capitol of Chi-Town some 200 years After the End, and 1 P.A. is the founding of the city. It is used to mark the end of the Second Dark Age, when Humankind began to rebuild civilization. The first book was set in the year 101 P.A, and subsequent Sourcebooks advanced the timeline to 109 P.A, which is 2395 A.D. Gregorian. Months and days appear to be unchanged. Hell, the fluff implies that the Coalition still celebrates Christmas.
• 7th Sea has a calendar that, like everything in 7th Sea, is strongly reminiscent of the one used in 18th century Europe with just enough cosmetic changes to make it more of a parody that a direct reproduction of the real world.
• Talislanta: A calendar year consists of seven months, each month lasting for seven weeks of seven days. Talislanta has seven moons, so it makes a certain degree of sense.
• Traveller: The calendar of the Third Imperium starts at the beginning of the reign of Cleon the Great. Notably, the founding year was designated as Year Zero, and years are generally just expressed as a (possibly negative) number. (1 AD is Imperial year -4520.) The official calendar has 365 days, numbered 001 to 365. Day 001 is a holiday; the other days are arranged in 7-day weeks, with weekdays Wonday, Tuday, Thirday, Forday, Fiday, Sixday, and Senday. There is an official Imperial Office of Calendar Compliance to insure that this calendar is kept up between worlds. Some have said that this doubles as a Secret Police.
• Warhammer 40,000: The Imperium still uses the Gregorian calendar, but the presentation of years is different: the current year as of this entry in the Gregorian calendar, 2018, would be written as "018.M3". However, the internal workings of the calendar is a bit different than the modern Gregorian Calendar. Take for example December 24th 2018: the using the Imperial dating system, this would be 0979018.M3 . The first number (0) means that the dated event took place in the Sol system, allowing perfectly accurate dating. The more inaccurate that dating becomes, due to distance from Earth and lack of information, the higher the first number will be, up to a 9 where there is no direct or indirect evidence and it is the closest possible approximation according to when the nearest Imperial Astropathic office received the news. The next three ciphers (979) mark the fraction of the year that has passed^note although this is only really used in bureaucratic records. The next three ciphers (018) are the year. The ending (.M3) is the millennium.
• Warhammer Fantasy Roleplay: The Imperial calendar counts the years from the coronation of Sigmar, an event marking the birth of the Empire (canonically the game is set in 26th century). The year is 400 days long and divided into 12 months with six with intercalary holidays on the Solstices, Equinoxes, the New Years Day and the cursed Geheimnisnacht where the border between reality and the Realm of Chaos is thinnest that changes exact location each year without breaking the lunar cycle outside of that day, while weeks are eight days long. The Empire took this calendar from the Dwarfs after the founding tribes couldn't compromise on any other method. Other nations use similar calendars, usually numbering the years from the founding of respective state (e.g. 977 IC for Bretonnia, 1524 IC for Kislev). And the calendar of High Elves is divided into epochs of variable length, each one referring to the reign of the particular Phoenix King (very similar to the Japanese eras). Wood Elves, Ungols and other nomadic tribes use various lunisolar calendars. On both New Years Day and Geheimnisnacht, both the normal moon and the cursed Chaos moon are always full, on the normal cycle on New Years Day and outside the cycle entirely on Geheimnisnacht. Also Geheimnisnacht isn't a holiday so much as everyone is too busy praying, fortifying defenses and making sure the local graveyards are properly being tended to. The latter is because the dead rising on top of the beastmen and greenskin attacks as they become driven to greater violence each Geheimnisnacht is a bit inconvenient.
• Wanderhome dictates campaign play through "the great arc of the year," which is divided into five seasons of two months each, with a holiday concluding each season. For example, the recommended starting season is Leap, the setting's corresponding season to late winter and early spring. Leap's two months are Tillsoil and Monsoon, and the season ends with the Sun Parade. Meanwhile, each year is given its own name, with the starting year being "The Year of the Waterlily," and subsequent year names being up to the players.

Video Games

• Cat Girl Without Salad:
  • As said in the Radical Galaxy after the Inbedia appear, and Kebako is surprised by the existence of numbered years, Squiddie relates that years stopped being numbered in "Back in Lemon Pop Donut".
  • Gunnar mentions the year Lemon Waffle Cronut.
  • The Collector's Edition Space Bounty Hunter License has Kebako's birth year as Pretzel Grape Chickenwing.
• In Civilization V, the Mayans use their own calendar, instead of the Gregorian calendar everybody else uses, upon discovering Theology. They also get a free Great Person every baktun, so this isn't a merely decorative effect.
• In Cytus II, the implementation of the Node system (a new method of subdividing the world's territories) marked the beginning of the New Age, advancing the era from A.D. to N.A.
• Destiny: One of the civilizations destroyed by the Hive was the Ecumene. It isn’t elaborated on, but their calendar measures time in “radial years” and “grooves”, so that the date they declared total war against the Hive was Radial Year 989 groove 3, and the date the war started turning against them was Radial 990 groove 0. It evidently resets at some point, since the Ecumene mentions being in contact with the Ammonite civilization 24,000 years ago, which is obviously much larger than the current Radial Year.
• Zigzagged in Disco Elysium. Centuries aren't numbered, but individual years within a century are. Past centuries are instead given a name based on the most significant event which occurred in them, while the present century remains nameless until it passes - thus, the current year at the start of the game is '51. The days of the week and months of the year do line up with the Gregorian calendar, however, with the game beginning on a cold Monday in March.
• The setting of Dishonored has 364 days split into thirteen 28-day months, with the 135th day, the Fugue Feast, not belonging to any month.
• The Dragon Age universe actually has multiple calendars. The most widely-used one is the Chantry calendar, which groups time into 100-years Ages, and which starts with the founding of the Chantry. In the year before a new age is set to begin, the Chantry look for portents to determine the name of the upcoming age, with the name reflecting major events that will happen during those hundred years. The title actually comes from the Chantry calendar (they declared the present age the Dragon Age). Years are written in chapter-verse style, since each one is a new chapter in the Chant of Light. Thus, the thirtieth year of the Dragon Age is 9:30, the age started at 9:1 and will end at 9:100. Events prior to the Chantry are said to be in the Ancient Age, with the year given in negative. The Tevinter Imperium has its own calendar that starts with its founding, and the elves have their own calendar that begins with the founding of Arlathan. See here for more info.
• An in-game book in Dungeon Siege hints at this; a guard's journal features such 30-day months as "Threb", "Smoth", and "Foth".
• Dwarf Fortress has a calendar with 12 months named after minerals, with each month being exactly 28 days long for a total of 336 days in a year. It counts from the start of world's generation and by default the playing time is 250, but can be edited. Additionally, the calendar counts Eras, first depending on how many titans, megabeasts and other of their ilk are still alive in the world, following into varying Eras of mortal races and potentially into Ages of Death or Emptiness if mortal civilizations got eradicated by something.
• The Elder Scrolls games have a system which is actually our own calendar system, but with different names for the months and days of the week. October becomes "Frostfall", Saturday becomes "Loredas", and so forth. The number of the year is determined by the amount of time since the beginning of that particular Era. Oblivion begins on the 27th of Last Seed (August) in the 433rd year of the Third Era, which began with the unification of Tamriel and founding of the Septim Dynasty and ended with the events of the game. Skyrim begins on the 17th of Last Seed in the 201st year of the Fourth Era, which began following the conclusion of the Oblivion crisis. To make things more confusing, the Eras vary between starting on year 0 or on year 1 (the First and Third Eras began at year 0, the Second and Fourth at year 1). There have also been mentions of different elven calendars (the Eras system is a human one, carried to continental prominence by the three Empires out of Cyrodiil), but none have actually been described (dates have been given in the Dwemer calendar, but without an explanation for what "P.D" stood for or any mentioned event that could be used to synch the Dwemer and Era calendars).
• Done by accident in Elite Dangerous: the in-game calendar is synced up with real-world time, but with 2014 corresponding to 3300 in-game, and as a result the leap years don't match up. This was referenced with a special quest for the leap year day in 2016 (3302 in-game).
• Etrian Odyssey has twelve 28-day months with names mostly themed after the Eastern Zodiac: Emperor, Dormouse, Taurus, Tiger, Lapin, Uroboros, Serpent, Stallion, Aries, Capuchin, Phoenix, Demiurge, ,and Khrysaor. Curiously, there is a thirteenth month after that, Summoner, that is only one day long, presumably just to add a 365th day to the year. The calendar does not tie into the series' lore; it's mainly just a flavorful way to say how many in-game days have passed since you started the game (after all, something like Lapin 14 or Aries 10 sounds cooler and more conductive to player Fanon than, say, "Day 55".)
• Escape Velocity Nova years use the suffix "NC", for "New Calendar". The game starts in 1177 NC; 0 NC was 2780 AD, the year FTL inventor Omata Kane died.
• EVE Online:
  • One of the EVE chronicles discusses how the four empires decided on a common calendar system. They ended up using the Gregorian calendar, and the date of the decision became January 1, year 0. The months of the EVE calendar match up with those in real life. Years are done a little differently; the year of the game's launch, 2003, corresponds with the in-game year 105. 2008 is referred to in-game as year 110.
• EverQuest II takes place in the year 500 A.K. (After Kerafyrm) starting the new calendar after the famous day when the powerfully insane dragon was woken up by mortals and went on a rampage against his own dragon-kind in the original EverQuest. Things get complicated when you try to compare it to the calendar that the first game used: There was none. Each server had its own in-game date, and always fluctuated during downtimes like patches and such. However, it doesn't stop there. During those 500 years between the two games, the Ogres rose up and built a new empire that tried to take over the world. Their own records of the 2nd Rallosian War are recorded in their own established calendar system. Over on the continent of Kunark, the evil Lich Venril Sathir built a new Sathirian Empire, using the ancient Sathirian Calendar themselves. None of these established calendars have any overlapping date of reference to pinpoint exactly when they take place on a universal calendar that the player can reference. This was done intentionally by the developers so they would have some leeway to fit in new events that happened during the 500 year period without conflicting with anything.
• Final Fantasy:
  • Final Fantasy Tactics uses a calendar based on the Western Zodiac. This was changed in the English PSX version to the Gregorian calendar, but kept in the PSP version.
  • Final Fantasy Tactics A2 has its own calendar, which is the regular one but with different names and twenty days for every month.
  • Final Fantasy VII uses Gregorian names for months, but February has at least 30 days. And the number of the year gets reset after each 2000-year Greek-letter "era", so 1999 of the Mu era was followed by 0000 of the Nu era.
  • Final Fantasy XIV's years are all derived from the Astral and Umbral eras, which are cycles of prosperity and disasters respectively. Some of these eras span thousands of years, while others are relatively short, with the Seventh Umbral Era dates from the unleashing of Bahamut from the Moon of Dalamud at the end of the Legacy timeline, while the Seventh Astral Era dates from the defeat of the Garlean forces by the Eorzean Alliance covered by the events of A Realm Reborn five years later. The months are calculated as six cycles alternating Astral and Umbral Moons, for a total of 12 moons. So the third month would be the 2nd Astral Moon.
• Fire Emblem:
  • The continent of Valentia in Fire Emblem Gaiden's remake, Fire Emblem Echoes: Shadows of Valentia uses a four-cycle calendar that corresponds to the four seasons (known as Flostym, Avistym, Pegastym, and Wyrmstym). As progress of the calendar from one season to the next is tied to how quickly one finishes the act that takes place within a particular season, each season can potentially have hundreds of days within it, although the in-game day tracker stops at 999.
  • The continent of Fódlan in Fire Emblem: Three Houses weirdly uses the Gregorian calendar, complete with leap year correction, and dated from the founding of the Adrestian Empire. Though the word “month” is used informally, the months are properly referred to as “moons” which are named after important happenings in the world during the month; a month in which aerial migration of wyverns is the main event is called Wyvern Moon, for example. The only major difference is that the first month of the year is the April equivalent (thought only relevant in-lore, for in-game purporses the game numbers the moons in the usual Gregorian order).
• Freelancer measures the years as "B.S." ("before settlement") and "A.S." ("after settlement"), with the arrival of the Liberty to Planet Manhattan as its zero point; days and months, meanwhile, are measured with our Gregorian calendar and our 24 hour days. In the popular Discovery modification, the calendar in House Gallia uses AGS, or After Gallic Settlement.
• The MSX Gradius series (a.k.a. the Nemesis trilogy) uses Gradian years, a calendar system which no other entries of the series used at the time. The original Gradius is set in the Gradian Year 6658, which is followed by Gradius 2 (aka Nemesis 2) in the Gradian year 6666 and Gofer no Yabou Episode 2 (aka Nemesis 3: The Eve of Destruction) in 6809. The MSX version of Salamander is also part of this chronology, being set in the Gradian Year 6709. This calendar system would later be implemented into the mainline series with Gradius V, which is set in Gradian Year 8010. The Wiiware game Gradius Rebirth is a prequel to the MSX Gradius 2, being set in Gradian Year 6664.
• Guild Wars has its own set of calendars, one for the Canthan continent, and one that is shared by both the Tyrians and Elonans. The Elonan calendar also has a zero year some two centuries before the Tyrian calendar.
• In Half-Minute Hero, the 1st year of the Goddess Era marked the first time the Time Goddess descended upon humans. Every game mode takes place at a different point in the Goddess Era.
• Harvest Moon/Story of Seasons:
  • Most of the games use years made up of four thirty-day seasons. The years themselves count up from the start of the game, which is usually when the player character arrives in town, which is always in the Spring.
  • The Rune Factory spinoff series takes this one step further by combining Saturday and Sunday into a single day called "Holiday", meaning that every day of the year will always be on the same day of the week.
  • Story of Seasons (2014) does the four seasons, but has 31 days per season.
  • In the Wonderful Life games as well as the remake Story of Seasons: A Wonderful Life there are still four seasons, but only ten days per season, with no designation for days of the week.
• Homeworld uses four calendars: Kharakian Dating System (KDS), Before Hiigaran Landfall (BHL), After Hiigaran Landfall (AHL), and Galactic Standard Year (GSY). The first three were used exclusively by the Hiigarans, while GSY, as implied by its name, is used by all other races. BHL and AHL are used in the same manner as our BC and AD, except for the use of year 0. KDS started in 1216 BHL, while GSY began in 9510 BHL. Confused yet? If so, then I would not even attempt to read this timeline. Strangely enough (or, more likely, so as not to confuse the players even more), all four calendars have the same length of the year.
• In I Was a Teenage Exocolonist, a year on Vertumna is a little longer than a year on Earth. It's divided into 13 months across five seasons: 3 months each of Quiet, Pollen, Dust, and Wet, and 1 month of Glow.
• Imperium Nova uses a 400-day calendar with ten months to keep things simple. Each galaxy numbers years based on the ascendance of the current Imperial house, which like the Japanese system can make long term dating difficult in certain galaxies.
• Kingdom of Loathing uses a 12-month calendar in which each month has 8 days. The first day of each month is when Ronald, one of the Kingdom's two moons, is full. The holidays that affect the goings-on of KoL are: KoL-specific holidays, which pop up only on their day of the KoL year; real-world holidays and other observances, which occur when they occur in our year (for example, our Friday the 13th causes things to happen there, even though KoL months don't have that many days to begin with); and parody holidays, which tend to happen both on a specific date on the KoL calendar and on the date of the parodied observance. This occasionally creates interesting scenarios where real holidays and their ingame versions intersect, including one memorable instance where Christmas (or Crimbo, as it's known in game) and the in-game Halloween coincided, or Drunksgiving, where the in-game holiday 'Feast of Boris' occurred on the real-life St. Patrick's Day.
• In Look to the West, the Societist Combine has its own "universal" calendar, since all existing calendars are based on the divisions between different peoples. The calendar counts from Monember to Dodecember, but in a bit of a fudge, Monember is actually March, so that September, October, November, and December can stay the same, but the year still starts in Undecember (January).
• The Metroid series uses "cycles" and subdivisions thereof for its calendar system. The only point of reference given is that the Galactic Federation officially formed in 2003 CC (Cosmo Calendar). What relationship, if any, the Cosmo Calendar might have to our own is never even hinted at.
• The D'ni calendar from the Myst franchise divides its year (hahr) into ten valleetee (~months) of 29 yahrtee (~days). As the D'ni civilization lived underground and on other Ages will disparate day/night cycles, they had little cause to align their calendar with surface-world days or lunar cycles. Note that the valleetee names translate to "lee one", "lee two", etc, similar to other cultures' "first month", "second month", and so forth.
• The freeware space exploration game Noctis puts the player in control of a cat-like alien creature called a Felysian, and employs the calendar of his civilization. For example the base unit, called epoc, corresponds to about 32 human years, but the smallest unit, the triad dexter (a billionth of an epoc) is "incidentally" equal to a second.
• Obduction features a town that was mysteriously teleported to an alien planet inside a protective bubble. Because the new environment has no obvious seasonal cycle, they opted for a system of just counting the days since their predicament started. When the town was renamed in honor of mayor Hunrath, the event also became the zero point of the calendar, so dates can be marked "Before Hunrath" (BH) or "After Hunrath" (AH).
• The Ogre series has the Zeteginean calendar, which corresponds to the Gregorian one for the purposes of allowing the player to choose a birthday, but is otherwise different.
• Dates in the two pre-Wii Paper Mario games are written with triangles and circles and stuff instead of names or numbers.
• A RimWorld year consists of four fifteen-day "quadrums:" Aprimay, Jugust, Septober and Decembary. Which quadrum corresponds with which season depends on whether you landed in the northern or southern hemisphere.
• In Roots of Pacha, one in-game year is composed of four 28-day seasons: Spring, Summer, Fall, and Winter. The game begins on the first day of spring, when the protagonist is adopted into the Pacha clan and settles in their village.
• The RuneScape calendar has 365.25 days like in real life but is instead split into 10 fictional months that last from 30 to 40 days. There also exists an "Old Saradominist calendar" which has alternative names for the seven days of the week but is considered archaic and the real-life days of the week are used in-universe instead.
• In Sid Meier's Alpha Centauri, a subversion: The game begins in AD 2101 and you presumably continue to follow the Gregorian calendar, but for whatever reason you now call them "Mission Years" (MY). One imagines that this is rather confusing to anyone on Planet who cares to think about it.
• SIGNALIS is set in an alien solar system which has been colonised by humanity.
  • You can find a diary, with the start date of 84-21-6, and the last number counting up. It also goes from day 9 to day A, suggesting that the date is in hexadecimal numbers.
  • You also find some medical records. All of the patients have dates of birth like "10S 62P a" or "29S 39P b." This is Rotfront style, which suggests that the other planets have their own dates.
• In Siren 2, the player can locate a calendar and other materials dated using the Japanese imperial system that begins a new count from the first year of a new emperor's reign. Strangely, all the documents use the "Showa" era, which ended in 1989 (Showa 64) even though some of the game takes place in "present day" 2008 (which in this case would be Showa 83). This should be the "Heisei" era, implying that the game takes place in a world where Emperor Hirohito ruled for at least another 20 years later than in reality.
• Soul Nomad & the World Eaters uses the Tamaito calendar, with the game taking place in the year 800.
• In the StarCraft expansion, the United Earth Directorate uses a different calendar, and the present year, 2501 AD (The original game used the Gregorian calendar), is marked as 872 GD. It's not explained what significance the year 1629 AD has to be year 0 on the UED calendar.
• Stardew Valley, which takes inspiration from Harvest Moon, uses 28-day seasons. While it does achieve the "years with identical week structures" effect that Rune Factory does without shortening the week, it also means that each year is 8 days shorter than in those two games.
• Officially, the year the Arcade game Strider is set (2048 A.D., as seen in the first stage's intro) was rebranded by the title's Big Bad as "Meio Year One", signaling the beginning of his rule. This was given a nod in the 2014 reboot, which is set in the year "Meio 0048", implying the game happens roughly half a century after Grandmaster Meio took over the world.
• Super Robot Wars:
  • Super Robot Wars Alpha series takes place in the New Western Calendar.
  • Super Robot Wars Compact, Super Robot Wars Compact 2 and Super Robot Wars Compact 3 takes place in 00XX.
  • Super Robot Wars Destiny takes place on Space Year 145.
  • Super Robot Wars Judgment takes place on Cosmic Era year 70.
  • Super Robot Wars T takes place in New Universal Era 200. however dialogue within the game, specifically mentioning that Tokyo Tower was built 700 years ago, gives it a rough placement using the Gregorian Calendar of somewhere in the mid-to-late 2600s.
  • The Super Robot Wars: Original Generation series starts around year 200 of the Space Era or New Common Era depending on which translation your playing.
  • Super Robot Wars 30 Takes place in year 100 of the New Space Era.
• Super Treadmill takes place during the 28-day month of Novtober.
• Swords & Souls: Neverseen uses fictional months to track time, like "Soulary" and "Soulmer".
• Syndicate gave its dates in N.C., simply standing for New Calendar. This added somewhat to the corporate dystopian feel of the game.
• Touhou Project, according to Curiosities of Lotus Asia, has two calendars: the official Gensokyo calendar that measures years as "seasons", starting from 1885 when the Hakurei Barrier was created, which uses the plain ol' Gregorian calendar but with traditional Japanese names (April, May and June, for example, become "Uzuki", "Satsuki" and "Minazuki"). There is also an unspecified youkai calendar, adjusted to natural phenomena like earthquakes or the blooming of bamboo flowers, which takes into account the youkai's extended lifespans, but few youkai actually use it.
• Wynncraft uses AP, or After Portal, with 0 AP being when the Nether Portal was first opened.
• In X, year 0 Argon Stardate is 2170 AD, twenty-four years after a Terran warfleet lured insane terraforming drones away from Earth, trapping themselves and the terraformers in the X-Universe. The fleet established their own society (called the Argon, after their leader Nathan R. Gunne), and erased all mention of Earth from their histories to prevent people from inadvertently leading the terraformers back to Earth. The games take place over 700 years later. The Terrans still use Earth's calendar, understandably.
• In both Xenogears and Xenosaga, humanity switches to the "Transcend Christ" calendar, with AD 2510 as TC 1. It is Gregorian apart from the new reckoning, which is the beginning of humanity's building ships to leave Earth and explore the stars.

Web Comics

• Aurora (2019) has a detailed calendar for its setting. The year is 380 days long and is divided into thirteen month-analogues, based on the orbit of the larger of the planet's two moons, with intercalary festival days in between.
• Children of Eldair: Eldair has 405 days in a year, and Koe mentions being familiar with several calendar systems, but is wholly unfamiliar with the date Embera, who's from Earth, gives as her birthday, March 21, 2002. She then has to give him the general idea when it is in relation to the Spring Equinox in the northern hemisphere.
• Cucumber Quest briefly demonstrates its rather... distinctive dating system in the characters' journal entries. Days are regular numbers, but months and years are listed in wingding symbols.
• The troll society of Alternia, introduced in Homestuck, measures years in "solar sweeps", with 6 sweeps equating to roughly 13 Earth years.
• Our World: The given year is 763, even though the story is set hundreds of years in the future, after The End of the World as We Know It.
• Sleepless Domain: The City uses an alternate calendar that labels years with the prefix "C.Y.", which presumably denotes the length of time that has passed since an event known as "the Collapse". The only specific date given is C.Y. 127, but as this date is mentioned in the context of a history lesson, there's no real frame of reference that can be drawn from it — this year might have been a decade, a century, or a millennium before the story begins.
• xkcd: In strip #2542 "Daylight Calendar", a new calendar system is implemented in which a "day" is counted as 12 hours of daylight, however long that may be, in order to provide extra time on deadlines. During November, the sun may rise and set as many as three times a "day".

Web Original

• The Chaos Timeline has the Sixtine Calendar (actually a subversion, since it's identical to the Gregorian), and ends up using 100 seconds per minute.
• In Land in the Stars, there are several, the most prominent being the "StarFall" calendar which begins on planetfall, year 0 SF. Which is when the Ancestors colonized the planets of Elys Aru.
• In the League of Intergalactic Cosmic Champions, the year 3000 is the Year 0 of the New Calendar.
• Taerel Setting: The Taerel calendar's amount of months is unknown, years are written as XE XXX, the first number (before the E) is the era number. The numbers after that are the year numbers. The Taerel calendar also has "ages" defined by technological progression. Ages have such names as "Stone Age" and "Shattering Age". Before that calendar was Retcon in there was the "B.P.D" calendar, X years Before Present Day. This did run into the problem of "how does it make sense" if you remember one would have to add a year each year that passed to all event dates.
• Orion's Arm uses the Tranquility Calendar described below in Real Life. The setting extends to 10601 AT (~12570 CE).
• In Shadowside, the world switched over from 2007 AD to 00 AED, "Years After Evos Dawn".
• Forest Bed, the setting of The Trader of Stories, has Blossomings (of the World Tree) instead of years and Breaths (also of the World Tree, which gives off light in day-like cycles) instead of days.

Web Video

• Dynamo Dream: There's a sign at the front of the Waterworks reading "est[ablished] 32". It's not clear what kind of era this was the 32nd year of, nor is any present date given to establish how long ago it was or what relation it has to our measurements. Likely a case of Hit So Hard, the Calendar Felt It.
• Hadriex created one of these for The Legend of Zelda: Breath of the Wild in this parody.
• The start of "Pikmin But Really Really Fast" has Olimar announce log entries with stardates involving special typographical characters. For example, the first scene is "stardate ampersand-carat-percent-dollar sign-dollar sign."
• Parodied in Scott The Woz. Scott hates the fact that first 23 days of December feel like filler, so he moved them back to a new month he dubbed "Bluth", with each day being its own "holiday" (such as "Why Is Scott Wearing That Hat?" Day and National "Shoot, Delaware's a State!" Day). The last six days of Bluth are simply labeled "Empathy."

Western Animation

• Implied in the 3-2-1 Penguins! episode "Practical Hoax" when Fidgel said that Bert Bertman was part of the class of 2222. Judging from the model of the car that Jason and Michelle rode in on their way to Grandmum's cottage, the show takes place at the dawn of the 21st century at earliest.
• In an episode of Doug, an extended fantasy sequence involving Quailman has a villain based on Mr. Bone, known as the Rulemeister, wipe out weekends from the timeline, forcing school students to attend school every single day (with no weekends on which to relax on). After Quailman defeats the Rulemeister by dropping a Logic Bomb of sorts on the Rulemeister, Quailman brings back weekends and adds an eighth day, "Funday", to the week, something that the narrator erroneously describes as "slowing down the Earth's rotation".
• On Family Guy, NBC invented Catillsday so they could have another Dateline.
• Futurama
  • One episode briefly parodies stardates:
    Zapp: Captain's journal. Stardate: uhhh...
    Kif: (sighs) April 13.
    Zapp: April 13... point two.
  • The intro to the episode "Game of Tones" has a scene captioned Flomuary 24th, 3013, followed by Flomuary 39th and March 2nd.
• On Jimmy Two-Shoes, all the months are named after Lucius. (Lucember, Lucapril, etc.)
• My Little Pony: Friendship Is Magic uses moons as a measurement of time, though it's never specified exactly how long this is. Common Fanon is that, much like other fantasy examples, one moon is equivalent to one month. Granny Smith mentions that it had been "over one hundred moons" since the last Apple family reunion, meaning about eight years had passed since the last one under this theory (assuming the same number of moons as in an Earth year).
• Samurai Jack: In Samurai Jack: The Premiere Movie Sir Rothchild scans Jack with his device to discover he originates from 25 BA (Before Aku), 25 years before Aku enslaved the Earth.
• The Simpsons:
  • The "Treehouse Of Horror VI" segment "Nightmare On Evergreen Terrace" had a flashback to a school board meeting on "the thirteenth hour of the thirteenth day of the thirteenth month. We were there to discuss the faulty calendars the school had purchased."
  Homer: (shivering) Lousy Smarch weather!
  • In "They Saved Lisa's Brain", the members of the Springfield chapter of MENSA claim control of Springfield's government after Mayor Quimby flees the town, and Professor Frink boasts of implementing metric time.
  Frink: Remember this moment, people, eighty past two on April 47th!
• The land of Mewni from Star vs. the Forces of Evil seems to have one; in "Mewnipendence Day", Star identifies the eponymous holiday as falling on "the 37th of Gravnogk". The Magic Book of Spells features a list of signs from Mewni's Fictional Zodiac, including their equivalent time-spans in Earth's calendar, which is full of more strangely-named Mewni months.
  • However, the show isn't always consistent with this. For instance, in "Escape from the Pie Folk", a character in Mewni dates a check with "July 30th".

Real Life

Currently used calendars

• The modern calendar used worldwide is based quite explicitly on Christianity, seeing as it counts upward from the date once accepted to be the birthdate of Jesus. This leads to interesting consequences among non-Christians who are kind of stuck with it:
  • Academics are prone to replacing the "BC/AD" naming scheme with "BCE/CE" ("Before Common Era"/"Common Era"). Part of the reason is that using "BC/AD" implies a tacit acceptance of Christianity — "BC" stands for "Before Christ", and "AD" stands for "Anno Domini" or "Year of Our Lord", both of which imply that Jesus is indeed the Messiah — and academia doesn't like to imply that religious doctrine is scientifically true, whether or not the academicians in question are Christians themselves. The other problem is that Biblical scholars generally don't think Jesus was literally born in 1 AD, but rather somewhere between 7 BC and 4 AD (probably one of the earlier dates, cross-checking against the death of Herod the Great ca. 4 BC) Using BCE/CE is actually Older Than They Think, being used in English as far back as the 17th century, though it has become much more common in recent decades. Funnily enough, even when BCE/CE is used by those who wish to avoid tacit approval of Christianity, it's a superficial change only, as all the dates are still based on the (traditional) birth year of Jesus Christ. It has just been in use so universally and for so long that Western Civilization is kind of stuck with it. Attempts to do away with it generally fall flat (see "the French Republican Calendar" below, as part of an attempt to completely dechristianize French society).
  • Muslims using this calendar use mīlādiy, meaning "of/after the Birth". This causes surprisingly few problems — most Muslims are actually fine with calling Jesus the Biblical Messiah (as long as you don't call him God), and the "Birth" doesn't necessarily have to refer to Jesus anyway.
• Some Christian congregations change the days of the week to use terms like "First Day", "Second Day", etc., because existing days have pagan origins — e.g. Thursday coming from "Thor's Day" and Saturday coming from "Saturn's Day". Schemes like this already exist in other calendars (including both the Jewish and Muslim calendars) and in many other languages as well.
  • Estonian and Portuguese languages have numbered days (esmaspäev, segunda-feira etc) for the week days, replacing the traditional names. Saturday, though are lauapäev and sábado (sabbath) and Sunday pühapäev and domingo (Lord's day)).
• Finnish language has names tammikuu (stem moon), helmikuu (pearl moon), maaliskuu (bare earth moon), huhtikuu (slash moon), toukokuu (sowing moon), kesäkuu (summer moon), heinäkuu (hay moon), elokuu (harvest moon), syyskuu (autumn moon), lokakuu (mud moon), marraskuu (death moon) and joulukuu (Christmas moon) for months. The names are descriptive on what happens during each month or what the month is like.
• Japan has traditionally reckoned its years by the reign of its various Emperors, or rather the era that corresponds with each Emperor — for instance, the current Emperor Naruhito's reign is the Reiwa era, and the year of his accession, 2019, is Reiwa 1. It's only really used in formal or special circumstances, but it's still used in random places (e.g. the Japanese patent system before 2000, which makes it a headache to search). This is also why Japanese computer programmers have their own Y2K problem every time the Emperor changes (again, most recently in 2019, when Emperor Akihito abdicated in favor of his son Naruhito). Interestingly, prior to the Meiji Restoration, the "era" didn't necessarily correspond to the Emperor's reign and was often totally arbitrary; the system formalized in 1872. There's also a much less used system counting up from the ascension of the legendary Emperor Jimmu in 660 BCE (one reason why Japan was so keen on getting the 1940 Olympics in Tokyo; it would have been the year 2600 by this reckoning).
• Many Orthodox Christian churches still follow the Julian calendar, which is thirteen days off from the Gregorian calendar, with the difference growing at a rate of three days every 400 years. Some have switched to the Gregorian calendar, while others have adopted the so-called "Revised Julian" calendar, which uses leap years slightly differently from the Gregorian calendar (although both calendars are in sync until 2800).
• Judaism uses a lunisolar calendar — i.e. a calendar that aligns with both the solar and lunar cycles. It's built around the New Moon as the start of each month, and counts years from the traditional Biblical date of the creation of the universe, meaning 2010 corresponds to 5770-71. The calendar uses a 19-year Metonic cycle (named after its inventor, the Greek astronomer Meton in the 3rd century BCE), adding leap months in a set sequence of years, in order to keep all Jewish Holidays falling in the same seasons.
• Buddhism similarly uses a lunisolar calendar that is similar to the Jewish calendar.
• Islam uses the Hijri calendar, which is a lunar calendar of 12 months and about 354 days. Because the lunar year is about 11 days shorter than the solar year, Muslim holy days usually shift 11 days earlier each successive solar year (even though they're always on the same day in the Hijri). It counts upward from the date of the Hijra, referring to The Prophet Muhammad's emigration from Mecca to Medina, and it's traditionally labeled "AH", from the Latin "Anno Hegirae". For example, AH 1433 was about 26 November 2011 to 15 November 2012 CE. (Interestingly, 20874 AH will be the same year as 20874 AD.) Only Saudi Arabia uses it for everything; everyone else in the Muslim world uses it only for religious purposes. For everything else, they use the Gregorian calendar, and many have done so for a long time — although what they call the Gregorian months can vary wildly from place to place, with some borrowing directly from Latin (e.g. Egypt and Morocco^note Which use different names from each other based on different readings of the (Late/Vulgar) Latin, interpreted through other languages (e.g. the Egyptian Dīsambar and Moroccan Dujanbir for December), some from other European languages (e.g. Algeria and Tunisia, which borrowed the French names wholesale^note For instance, January in both countries is Janfi, an Arabicised French Janvier), and others inheriting the pre-Islamic names (e.g. Iraq and the Levantine countries follow the Assyrian calendar, which has the same origin as the Jewish calendar), while still others using a mix (Turkey has a very weird naming system for the months, thanks to being a melting pot of European, Middle Eastern, and its own indigenous Turkic cultures. For example, April is called Nisan, borrowed from the Assyrian calendar; August is called Ağustos from Latin; while December is called Aralık, from the Turkish word for "corridor". The Turkish names for the days of the week are equally weird for the same reason).
• The Iranian calendar, used in Iran and Afghanistan, can justifiably claim to be both one of the oldest and newest calendars in wide use. The Iranians have had a unique calendar of some sort for as long at they've been around, which is at least 700 BCE. At least one such calendar remains the official calendar for Zoroastrianism, and the current calendar draws on innumerable ancient sources for its accuracy. But the latest version is based on principles laid out in 1079 CE and was only adopted in its current form in 1925. It combines the calculation of the Hindu calendar (including a highly complex system of calculating leap years) and the traditional Iranian calendar centered around the ancient spring festival Nowruz, sometimes called the "Persian New Year". However, Islam being prevalent in modern Iran and Afghanistan, it counts up from the Hijra like the Muslim calendar — but it's a solar calendar, which is why it's sometimes called the "Solar Hijri" calendar. Persian year 1390 is 2011-12 CE (a good 42 years off the equivalent standard Hijri year).
• Ancient Egypt had a calendar that's still kinda used in some places. The original calendar has long since faded into obscurity, but a variant has been used for centuries by the Coptic Orthodox Church as the Coptic calendar. Augustus Caesar modified it to be in sync with the Julian calendar, but that's about all that's changed since the days of the Pharaohs. It has twelve 30-day months and five monthless days, each day of the month having its own name. It was built around Egypt's unique agricultural situation, including the very regular rains and flooding of the Nile, to the extent that even the Muslims used the Coptic calendar for agricultural purposes until the 19th century. The Coptic calendar's epoch is 284 CE, the year of the accession of the Roman Emperor Diocletian, who was known as a persecutor of Christians — that's why it's traditionally rendered "A.M.", for Anno Martyrum — "Year of the Martyrs". A variant of the Coptic variant is traditionally used in Armenia, this one counting up from 552 CE.
• Most natives of the Arctic Circle have traditionally described the passage of time in terms of "sleeps", as the actual duration of any given day varies too widely at high latitudes to be a reliable measurement. Polar expeditions have to deal with the same thing, and as the natural circadian rhythm doesn't quite line up with the 24-hour day they're used to, things can get weird for those guys.
• North Korea uses the "Juche calendar" — Juche being the state philosophy of self-reliance (i.e. we'll do everything ourselves, thank you very much) — which counts upward from 1912 CE, the birth year of Kim Il-sung. All dates before then still use the Gregorian calendar.
• China would traditionally render its years by the reign of the Emperor, but now that there are No More Emperors, it's out of date on the mainland. But in Taiwan, they still use its logical variant, the "Minguo calendar" (or Republic calendar), dating upward from the foundation of the Republic of China in 1912 (which, by a stroke of coincidence, aligns it with the North Korean Juche calendar). In 2011, this led to the "Y1C Problem", as Taiwanese computers struggled to deal with the impending Minguo 100.
  • Taiwan and China also use the lunar calendar for the main holidays. They're adjusted to the solar calendar so Chinese New Year always falls at the end of January/February, Dragon Boat Festival some time in June, and Mid-Autumn Festival near the end of September.
• Computers often have their own internal reckoning which they then convert to human dates:
  • Most software uses "UNIX time", counting up the number of seconds (or milliseconds) since 1 January 1970, known as the "UNIX epoch". It's kept in sync with UTC, which uses occasional leap seconds to keep it consistent within a second of Greenwich mean time, so its value is not exactly equal to the number of seconds elapsed since then. Interestingly, this led to a Y2K-like phenomenon known as the "2038 problem", referring to the year when a signed 32-bit integer will overflow when reading UNIX time (but most systems nowadays are 64-bit, which would last you about another 300 billion years).
  • Basic programming stores dates as a double-length decimal number representing the number of days since 1 January 1900. It's easy to see if you use Excel or Access, because if you accidentally convert a small number to a date it will give you a day in 1900, and it's also how you can add whole numbers to dates. It doesn't, however, take into account daylight savings time.
  • Similarly, GPS time is measured in seconds since 6 January 1980. However, GPS clocks do not recognize leap seconds, which means that all efforts to convert a GPS time to a UTC time or vice versa require knowledge of when said leap seconds occurred to compensate, otherwise the computation will likely be off by a few seconds.

Historical calendars

• The French Revolution, wanting to change as much as it could, changed the calendar as well. The French Republican Calendar (Calendrier Républicain) was a way to eliminate the old Roman-derived religious calendar and replace it with something logical. Its epoch year was 1792, it counted up from year I in Roman numerals, and the years began on the autumn equinox. It only lasted for twelve years, and even then quite a few people never bothered to use it to begin with. Among its quirks:
  • It was a metric calendar (of sorts), with weeks made up of ten days rather than seven. Each month was three weeks long, and there were twelve months in total, leaving five or six extra holidays at the end of the year. The ten-day weeks were highly unpopular, as this eliminated quite a few weekends — the Concordat of 1801 restored the seven-day week and re-established Sunday as a weekly festival.
  • The names of the months and days of the week were changed, most of them referring to revolutionary or agricultural concepts. Similarly, individual days were also given names along these lines, a sort of secular version of the days given to saints in the old calendar. This led to days like "Pig Day" (Frimaire 5) or "Manure Day" (Nivose 8), which you probably didn't want to be your birthday. For the most part, these dates only survive when referring to important events in the Republican era, many of them coups of some sort (e.g. the "Law of 14 Frimaire", which centralized power in the hands of the Committee of Public Safety; the "Thermidorian Reaction", which essentially brought an end to the Terror; the "Coup of Fructidor"; the "Coup of Floréal"; and the "Coup of Brimaire", in which Napoleon first seized formal political power) — although the dish "Lobster Thermidor" also refers to the old Republican calendar (the month of Thermidor being around July and August), being named for an 1891 play set against the Thermidorian Reaction.
  • The calendar also came with a metric day, which divided each day decimally — ten hours per day, 100 minutes per hour, 100 seconds per minute.^note This means that there are 100,000 seconds in a Republican day, as opposed to 86,400 seconds in a standard day, and that a Republican second is accordingly 86.4% as long as a standard second. Hardly anyone used it, even in the government, and it quickly fell into obscurity.
  • Occasionally, you have people nowadays who use the Republican reckoning. Many of them are War Reenactors, some of whom still print calendars for the current year in Republican time. The French Floréal-class frigate fleet also bears the names of Republican months. The Paris Commune of 1871 (or rather, Year LXXIX) restored the French Republican calendar during its brief existence.
  • The Republican calendar formed the basis of the Positivist calendar, proposed by philosopher Auguste Comte in 1849. Much like the Republican calendar, it renamed the days and months to be less religious, this time naming them after "great men" from all walks of life, religious and secular. It had 13 months of 28 days each, which allowed every day to fall on the same day of the week every year, but preserved the seven-day week; it also had an extra "weekless" day every year, plus a second one on the leap years. Oddly, its epoch year was 1789, earlier than that of the Republican calendar. It never saw widespread use, but it did form the basis for the equally obscure "Tranquility calendar" seen below.
• The Soviet Union tried a new calendar in the early 1930s — almost a given, considering how the "secular-agricultural" naming scheme of the French Republican calendar seems like such a Soviet thing to do. That said, contrary to popular belief, it did retain the Gregorian months, and it still counted years in "BC/AD" as well. The calendar had five- and then six-day weeks, the idea being that weekends would be more frequent, and different industries would get different days off. Even the authorities doubted whether it was really necessary, and it lasted even shorter than the French Republican calendar.
• China used decimal time, similar to the French Republican clock, throughout its history before the 1912 revolution. The adoption of the Western calendar is widely considered a step backwards in China.
• Fascist Italy too had its very own calendar, in which 1922 marked the year zero; therefore, 1936 became XIV E.F. (that is, the fourteenth year of the "Fascist Era"). Remnants of this calendar can still be seen on the façades of many public buildings throughout Italy.
• Those Wacky Nazis tried to replace the Latin-derived months' names with more "Aryan" ones. This was the brain-child of Georg von Schönerer, a late 19th-century anti-semite and far-right radical from Austria, and is from long before the Nazis' time.
• When Muammar Gaddafi ruled Libya, he changed the Gregorian calendar with names of the months made up from whole cloth. Some could be understood as marking the changing of seasons, but others had no apparent rules (August was named after Hannibal Barca, whose Punic state covered parts of modern-day Libya, including the capital Tripoli). It also counted from the death of the Prophet Muhammad, instead of the birth of Jesus. The calendar was abolished in 2011 when he was overthrown, but with the country still busy resolving its civil war and the existence of several different standards in the region (at least in terms of naming the months), nobody could agree on what to replace it with.
• In Cambodia, dictator Pol Pot established a new calendar with "Year Zero" at 1975, the year he seized power. "Year Zero" became a buzzword for a total reset of Cambodian society — one which led to the deaths of millions of people who opposed him.
• The modern Gregorian calendar is based on the ancient Roman calendar, which had its own quirks at the time. First, its original version only had ten months, with January and February not really kept track of and just called "winter days" (this is why, for instance, October is the tenth month of the modern year despite the word literally meaning the "eighth month"). Second, years were traditionally reckoned by the reigns of the rulers in question. In the Republican era and early empire, years were named for the two consuls (there was a joke that the year Julius Caesar was consul, 59 BCE, he so overshadowed his co-consul Bibulus that it was known as the "Year of Julius and Caesar"), while most of the Roman Empire rendered years by the reigning Emperor. Interestingly, one can say that the modern Gregorian calendar follows the same logic (if you consider Jesus the "King of Kings"). Historians writing about Rome — both at the time and more recently — sometimes use the alternate system "A.U.C.", for Ab Urbe Condita, meaning "From the Foundation of the City" — i.e. counting up from the year traditionally used for the founding of Rome, 753 BCE (when it was actually founded is the subject of debate).
• Turkmenistan infamously renamed its entire calendar in 2002, including the days of the week, according to the whim of its leader, Saparmurat Niyazov, a.k.a. the Turkmenbashi, who was somewhat insane and almost certainly the administrative assistant to the Mayor of Cloudcuckooland. It's therefore probably not a coincidence that many days and months were renamed after himself and his family members. After he died, these changes were reversed almost immediately.
• In Ancient Greece, every polis had its own calendar, all of which were pretty darn quirky. They named their years after their government officials (like ephors in Sparta or archons in Athens). The Athenian political calendar had ten months, which allowed it to interact with the Athenian constitution (as Athens was divided into ten tribes, so one tribe a month had to have its representatives in the Boule stay there day and night to be on call for a crisis), but its festival calendar (used for religious and agricultural purposes) was a 12-month lunisolar calendar, and every other state had a different (and similarly crazy) scheme. Some historians tried to cut through this by using Olympiads, based on the Olympic games.

Proposed, niche, or joke calendars

• Of the many proposals for reforming the Gregorian calendar that have been made over the years, two have come particularly close to adoption:
  • The International Fixed Calendar divides the year into 13 28-day months, plus one extra day at the end of the year outside the weekday cycle (and a second in leap years between June and the new month Sol). George Eastman of Kodak was a proponent, and a 13-period calendar was in use internally at Kodak until 1989.
  • The World Calendar divides the year into 12 months in a 31-30-30 pattern, plus one extra day (and another in leap years). This proposal was seriously debated at the United Nations but was eventually dropped mainly due to religious opposition.
• The Tranquility calendar, first postulated in Omni magazine, is a 13-month revision of the Gregorian calendar, with the 1969 moon landing as its zero point — specifically, the exact moment that Neil Armstrong said "tranquility" in "Houston, Tranquility Base here". This creates an epoch second, so one can have an accurate measure of any specific point in time. Much like the Positivist calendar, there are 13 months with 28 days each, and all months are named after scientists. It adds one day every year outside the month and weekday cycle, Armstrong Day (20 July in Gregorian reckoning — i.e. the date of the moon landing), with Aldrin Day (29 February) treated the same in leap years. Dates are rendered "B.T." ("Before Tranquility") and "A.T." ("After Tranquility"). For example, 5 May 2013 corresponds to 21 Kepler 44 A.T.
• The "'Pataphysical Calendar", the calendar created by the Society of 'Pataphysics, is a parody of the Positivist calendar. It has 13 months made of 29 days, the last of which has no weekday and is imaginary most of the time anyway. It counts up from the birthday of the founder of 'Pataphysics, and its days are named after (among others) Don Quixote and Hari Seldon.
• There have been several attempts to create calendars for other planets and moons in the solar system, in case we need to live there someday.
  • The most developed is the Darian calendar for Mars, which has 24 months of 27 or 28 Martian days each (called sols, so we don't confuse them with Earth days^note JPL and NASA already use sols in tracking Mars missions: the activities of rovers are reported as, say, occurring on sol 43 since that rover landed.). There have already been arguments on what epoch to use (i.e. when Year Zero was); the Darian currently uses the "Telescopic Epoch", which is the Martian year corresponding to March 1609—January 1611 CE (when it was first sighted by telescope), but it originally used an epoch based on the landing of Viking 1 in 1976.
  • The same guy who did the Darian calendar has also proposed several for the Jovian moons:
    • Io: 24-month year, with 32 "circads" (fractions of the solar day that each roughly correspond to the length of the human wake/sleep cycle) per month, an 8-circad week, 40 circads in the twelfth month (and the 24th month in leap years). Callisto uses the same reckoning.
    • Europa: 24-month year, 8-circad week, with 32 circads per month, plus a week in month 24 in leap years.
    • Ganymede: 24-month year, 8-circad week, with 32 circads per month, minus one week in month 24 in non-leap years.
• Discordianism uses a calendar divided into five 73-day seasons (called Chaos, Discord, Confusion, Bureaucracy, and Aftermath), each with five-day weeks (Sweetmorn, Boomtime, Pungeday, Prickle-Prickle, and Setting Orange). Each season has two holidays, one on the fifth day and one on the fiftieth. It counts upward from 1166 BCE, so 2010 CE would be 3176 Year of our Lady of Discord. Every fourth year includes a leap day analogue called St. Tib's Day, but this has caused some unintended mathematical confusion as to whether this is meant to align with the Gregorian or Julian leap day (this being the Discordians, the answer is probably "yes").
• Maya "Starhawk" Greenwood, in her book Truth of Dare, introduced a tongue-in-cheek neo-Pagan calendar based on the weather patterns of San Francisco. This is why the three full moons of summer are called "Fog Rolls In Moon", "Fog Sticks Around Moon", and "Fog Sticks Around Some More Moon". In her fiction novel The Fifth Sacred Thing, the largely neo-Pagan community in San Francisco uses a variant that calls August the "Third Foggy Moon".
• The Human Era or Holocene calendar, defined as starting 10,000 years before 1 CE (which is now off by several centuries from when the Holocene started) was first proposed in 1993 and designed to begin close to the start of human civilisation. Kurzgesagt discusses it in this video, and publishes a Human Era calendar every year.

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