Universal Universe Time

"US Naval Observatory Master Clock. Eastern Standard Time, 2 hours, 1 minute, exactly. Universal time 7 hours, 1 minute, 5 seconds."

— For a Good Time, Call...

In most science fiction stories, although it is an issue that is seldom even touched upon, it appears that the entire Universe uses the same timekeeping and calendar system as Earth - years, months, weeks, days, hours, minutes, seconds, etc. Most planets also apparently experience a day/night cycle that is practically identical to that of Earth.

This is, of course, completely ignoring the fact that in the real world, the calendar and timekeeping methods we use here on Earth would, almost without a doubt, totally not work at all for 99.99999% of all the other planets in the universe. Because, surprise, surprise, planets orbit their stars at their own unique speeds, and they rotate on their axes at different rates, too, both of which are influenced by a large number of factors and can range from nearly static to extremely fast.

Just to put it in perspective for you: One "day" on Venus, our closest neighbor planet, is equivalent to approximately 117 Earth days because its rotation is so much slower than ours. On the other hand, one "year" on Venus is equivalent to 225 Earth days because Venus moves a bit faster, and its orbital path is shorter than Earth's. (The 243 Earth days figure you may see bandied about as the length of a Venusian day is its sidereal day. The mean solar day is shorter due to Venus's retrograde rotation, whereas planets that rotate prograde have a solar day that is longer than the sidereal day^note in any case, the effect only becomes large if the siderial day length is a significant fraction of the year length; eg, Earth's discrepency is approximately ~4 minutes.) It gets weirder — one Mercurian day is about 176 Earth days, or precisely two Mercurian years. (The precise 1:2 ratio is due to a 3:2 spin-orbit resonance.) Yes, that's right — on Mercury, a day is two years. (Feel free to speculate about whether dates like April p.m. have any meaning.)

And this is before you take relativity into account: depending on gravity and velocity, time can actually proceed at different rates at different points in the universe. This means that planets with different orbital velocities and gravity will experience time at different rates than Earth.

When this occurs (even more bizarrely) in a Time Travel story, it's San Dimas Time and/or Meanwhile, in the Future….

A Sub-Trope of Standard Time Units. Sister Trope of Implausible Synchrony (all clocks show the exact same time of day). Compare Time Zones Do Not Exist. Contrast Two of Your Earth Minutes, the standard Hand Wave to get around this.

Usually falls into the Acceptable Breaks from Reality category, because Most Writers Are Human. Sometimes Hand Waved (or at least assumed by fans) to be a result of whatever makes us hear them in English.

To learn more, visit the analysis page.

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Examples:

Anime and Manga

• Averted in ARIA, which takes place on a terraformed Mars called Aqua, they explicitly mention Aqua's longer year.
• Averted in Galaxy Express 999. It's an important plot point at times—the 999 stops for whatever constitutes a 'day' on each station's planet, and then leaves, missing passengers be damned. This is explained to the protagonist as early as the second episode of the series.
• Apparently played straight in Legend of the Galactic Heroes, wherein the entire Milky Way Galaxy seems to operate on one standardized time zone.
• Averted in the Mobile Suit Gundam Wing novel Frozen Teardrop, which takes place on Mars. Though Mars' day is roughly the same length as Earth's (being only 37 minutes longer), its year is twice as long. This leads to Mars using a different calendar (MC, with MC 00 = AC 182, when the Mars terraforming began) from Earth, based on the Martian year. Mars dates are correlated with Earth's by the use of Earth's seasons, with Martian years divided into eight seasons to correspond to the seasons on Earth.
• In the first episode of Bodacious Space Pirates Misa consults a watch that measures Galactic Standard Time, and finds that it rolled over to the next day during dinner.
• Zig-zagged in Coyote Ragtime Show. Days and weeks are the same galaxy-wide, which is important as the plot revolves around a week-long race against time, and years appear to be the same, too. However, there isn't just one Alternative Calendar in use; there are multiple named, presumably used by different planets.
• Justified in Venus Wars: as Venus' day is much longer than Earth's, the colonists use Earth time measurements for comodity.

Comic Books

• Averted, in all places, in many Disney Mouse and Duck Comics stories:
  • In Mickey Mouse Frontier Chronicles, humans use the same hours, minutes and seconds as they do on Earth, but it was mentioned that days and years depend on the individual colony, even specifying that Earth-32's year is 328 local days long.
  • In Paperinik New Adventures most aliens go by "time units". The exception was the Evronians, who were (eventually) given their own time measurement system. Said system was originally intended as a joke and part of a gift for a special issue (a calendar, with the year divided in both Gregorian and "Evronian" years), but was eventually used in the actual series starting with the Xadhoom Trilogy.
• This is played straight in Albedo: Erma Felna EDF, when all the dates, regardless the planet the characters are in, are stated in a single unified calendar, the Standard Calendar (SD). There's no explanation for planet-specific time measures in the comic, through.

Fan Works

• Lampshaded in the Spirits Of The Force series of Star Wars fan films. In the second installment, Kyle asks Jan about the time, and Jan replies telling him the standard time on Coruscant. Then Kyle asks for CURRENT time. Jan looks back. Beat. "We're in SPACE."
• Bait and Switch (STO): Averted.
  • From Bajor to the Black gives the current date by both the Federation (i.e. Earth) and Bajoran calendars.
  • In The Wrong Reflection, Eleya's hometown in Kendra Province is shown to be in daytime, but it's nighttime in the capital city of Ashalla.
• The War of the Masters conventionally gives its dates by Earth calendars, but times are given locally (Starfleet-operated space stations and ships still use GMT for timekeeping, though), and some planets have their own calendars.
  • In stories set on Moab III, such as In the Presence ofHeaven, Would You Choose Hell?, the locals have additional hours on their daily clock due to Moab's slower rotation.
  • A Good Compromise gives both the Trill date and the Earth date.
  • In Create Your Own Fate, Eleya is woken up on a lazy weekend morning in her apartment in Kendra City, but it's after midnight in Hathon. However, Hathon is a major business center and is up and running 26 hours a day.
• A minor plot point in The Next Frontier. When the Kerbals send their first FTL starship to another star system, they quickly realise it's inhabited by an advanced spacefaring culture after their long-range telescopes spot eleven separate planets and moons with an oxygen atmosphere, far too many to be anything but the result of terraforming. Once they set about recording the local TV broadcasts to learn about their neighbours, it's noted that once the linguists back on Kerbin have worked out how to read the local numeric system they can work out how long a standard local day is, and therefore which habitable planet is their original homeworld. It eventually turns out that none of them are, and they've run across someone's Lost Colony.
• Averted in Rocketship Voyager. The clocks on the eponymous rocketship have two dials—one set to the atomic clock on the Computer Deck (known as Shiptime), the other adjusted to the Standard Time of the nearest space station or planetary LowPort. When they end up on the other side of the galaxy, they also have to convert alien measurements of time to something they're familiar with.

Film

• Avatar doesn't ever bring up the day and night weirdness that would come with living on a moon orbiting a gas giant in a binary star system. On the other hand, camera recordings display a date in day, month, and year in Earth time. Differences in the days, as well as the effects caused by the proximity to the gas giant Polyphemus on the day-night cycle has been addressed in both the wiki and the Activist's survival guide.
• In Men in Black, a galactic standard week is an hour. The 37-hour day the MIB runs on is a specific alien culture's time system—presumably the first species MIB encountered.
  Agent Zed: You'll get used to it. Or you'll have a psychotic episode.
• Averted in the Firefly movie Serenity. When Inara contacts Mal about her "local trouble," she mentions that it's cool where she is, since Autumn is starting at her location on the Companion planet.
• In King Dinosaur, the scientists exploring planet Nova decide to use Earth time despite knowing that Nova's day-night cycle is likely different.
• In Interstellar, the protagonists keep a close eye on Earth time, even as they pass by areas that suffer from Relativity weirdness. This adds dramatic tension as they watch time pass by that their planet is running out of.
• Averted in Turbo: A Power Rangers Movie of all places. Divatox calls Rita Repulsa (on a phone) for advice on how to deal with the Power Rangers. Rita is if not still on Earth's moon then certainly in somewhere in space, and is explicitly shown to have been woken up by the call. Divatox even apologizes, saying she forgot about the time change.

Literature

• Crest of the Stars has at least one planet with an odd example. Since it was terraformed and opened for colonization by the space faring Abh they just used a single timezone with a 24 hour day that ignores the local day/night cycle, so 11 in the morning could be sunset, sunrise or the middle of the night depending on where on the planet you are.
• Thoroughly averted in the Red Mars Trilogy by Kim Stanley Robinson, where the calendar requires some rethinking. The year is 669 sols long (that's Martian "days", by the way). The year is divided into twenty-four months, each 28 days long, with every eighth month being 27. They deal with this by using the name of every month twice, prefaced with 1 or 2 depending on which half of the year it is. They also measure the year in degrees for simplicity's sake, with the Spring Equinox being used for 0/360. The seasons are six months long. Oh, and Martian sols are about 24 hours and 40 minutes. They don't bother reworking the timekeeping system though, they just stop the clock for forty minutes at midnight (they call this the "Timeslip", and it becomes one of the first major cultural differences from Earth, gaining a reputation as a sort of "witching hour" where certain social mores are briefly suspended).
• It's noticeably averted in Charles Stross' books Singularity Sky and Iron Sunrise, where it's acknowledged that FTL travel would make a form of time travel possible if a super-powerful AI didn't outlaw it.
• In Accelerando by Charles Stross. Space travel within the solar system leads to a time system of seconds, kiloseconds (16 minutes, 40 seconds), megaseconds (11.57 days) and gigaseconds (31.7 years).
• Averted in Marion Zimmer Bradley's Darkover books, where the local clock uses a 28 hour day. Presumably, the inhabitants of the Lost Colony initially used Earth hours, and their descendants forgot the reason.
• The Qeng Ho in Vernor Vinge's A Deepness in the Sky avert this by using a time system based on orders of magnitude of seconds. Still arguably applies, though, if only because their system is the standard universal one. It also has its zero point set at the Unix epoch — 00:00:00 UTC on 1 January 1970. In universe it's believed to date from the first lunar landing.
• The Hegemony of Man from Dan Simmons' Hyperion Cantos uses a standardized day. Thanks to the Farcasters the time is the same everywhere in the galaxy at all times. When the protagonist ends up on the long lost Earth or maybe a recreation of it he's pleasantly surprised to find that the day night there happens to match one standard day, something he's never experienced before.
• In Isaac Asimov's Foundation Series as "evidence" for the theory of humanity originating from one planet, when Earth is lost and forgotten. Not that everyone accepts this explanation for the length/number of hours, days and years.
• The Honor Harrington series addresses this in a appendix to the first book. Every planet has its own clock and calendar, usually with a period after local midnight called compensation or 'comp' to deal with days not having a whole number of hours. Local years are divided up into (fairly arbitrary) number of months. Everyone uses Earth dates for international time-keeping, usually expressed as T-years, though in the Post-Diaspora calendar. Since the Star Kingdom of Manticore contains three different inhabited planets with wildly varying calendars, time conversion software comes standard on their computers.
  • Except Grayson which, being colonized by an arch-traditionalist Luddite cult, uses Earth time units in spite of them being nowhere near suitable for the planet's rotational and orbital times. To top it off, they are the only culture that still uses A.D. to mean Anno Domini rather than Ante Diaspora.
  • More or less ignored as the series grows more complex and the Technobabble is replaced with political intrigue.
  • Weber's Safehold series (which, pre-Gbaba, bore several resemblances to the Honorverse) renamed 'comp' to "Langhorne's Watch". It served the same purpose as comp, namely making Safehold's 26 hour 31 minute day match up with clocks calibrated to Old Earth seconds and minutes, but co-opted the "extra" time to the service of the Church of God Awaiting since they couldn't admit humans had ever lived on another planet.
• Averted in the Vorkosigan Saga, where characters at least occasionally mention things like it being "18:00 hours of a 26.7 hour day [on this particular planet]".
• Subverted in In Robert A. Heinlein's Stranger in a Strange Land: the main character, early in the book, notes to himself that the flow of time on Earth is different from his birthplace of Mars.
• Played straight for the most part in Andrey Livadny's The History of the Galaxy books, where everyone in the Confederacy of Suns uses the same years. Months and days are, conveniently, almost never mentioned. The years are, of course, standard Earth years, even though Earth isn't even a part of the Confederacy thanks to The War of Earthly Aggression that led to the Earth Alliance being defeated by the Free Colonies, which re-formed into the Confederacy. Subverted in one novel where an alien supercomputer asks how long it has been off-line, and a human replies that it has been over 3 million years, causing the computer to prompt for the definition of a "year". The human defines it as one full orbit around a star, prompting the computer to ask for further clarification as to the parameters of such an orbit. This stumps the human, as she has never thought of this. The computer then simply searches her mind and finds enough information about Earth to scan its own database for it. Of course, this fails to take into account that the database is 3 million years old, and Earth's orbit has changed since then.
• The Dirigent Mercenary Corps series uses an interesting solution. They lengthen the second to make a Dirigentian day 24 hours.
• Adverted in Embassytown by China Miéville where, given the number of planets colonized, time is mostly given in Kilohours. When the narrator does talk about years, they turn out to be about 3.5 earth years long.
• John Varley's novel Red Lightning mostly takes place on Mars, which has a day that is 24.622 hours. The Martian settlers chose to make the day 24 hours by stopping the clock for the 0.662 hours.
• Averted in Ian McDonald's Desolation Road, which has human characters being considered fully mature adults and going off into the world at the age of ten. Ten Martian years, which is a tad over 18 earth years.
• Mass Effect: Revelation states that although different species' days vary considerably in length, their years are all roughly the same length as an Earth year. The Citadel species all evolved on planets orbiting suns similar in size to Sol, which restricts the location of the habitable zone, meaning the range of distances at which their homeworld can orbit and support life. This in turn dictates the length of the year, because the speed of a stable orbit is dictated by the force of gravity, which is a universal constant.
• In Captain French, or the Quest for Paradise, this tends to be averted for all colonized planets. However, aboard the Circe, French keeps to standard Earth time and gives all time measurements in standard days, months, years, etc. The topic is expanded, when he speaks of Solaris, whose period of rotation is equal to 15 hours (at the equator). Try as they might, the Solarians have not managed to get used to such a short time period, as there simply wasn't enough time in a day, while a two-day cycle would've been too long. Instead of trying to adjust the planetary rotation speed (which would've probably ended in a disaster) or messing around with whatever genes force us to sleep for 8 hours and stay awake for 16 (also a likely disaster), they have implemented a brilliant social measure that appears to work for everyone. Every Solarian belongs to one of five clans, differentiated by colors of clothing. Each clan lives on its own time, shifted by several hours from the next one. Small settlements typically belong to the same clan, while cities are split up into districts. This works out for anyone who might want to enjoy the "night life", while his own clan is deep asleep. All he has to do is go to a neighboring district, where the "night" is still young. The clan split is cosmetic at best, as there are no social taboos against intermixing or switching clans. Think "time zones" that are not geographic in nature.
• In Xandri Corelel, everyone seems to measure time in hours. The standard day used by starships is twenty-six hours long; Cochinga's days are twenty-seven hours.
• In This Alien Shore, time is measured in E-days, E-years, and so on.
• Star Wars Legends:
  • The Galactic Republic (and the later Galactic Empire) uses a 368 day year calendar that uses the capital planet, Coruscant, as the standard, though mostly on Fleet ships and for the purpose of scheduling. Other notable deviations from the Earth calendar includes a 5 day week and a 7 week month. Early EU material mentioned 10-month years, but this later became 12 for general understandability. Five times seven times twelve gets you more than three hundred sixty-eight. It's ten months, plus a few holidays and festival weeks that don't belong to any month...which is even worse to try to remember than just ten months. The Hyperwave Transciever and Subspace Radio is what allows standardized time, which gives them literally instantaneous communication between any two places in broadcast range. When a communications relay in a strategically important location is destroyed and a message needs to be sent there in the New Jedi Order series, this becomes a plot point. As the second-fastest thing the protagonists have after the currently-down instant communications, a starship—the Millennium Falcon, naturally—gets sent to deliver the message instead. This opportunity is conveniently used to deliver some exposition about how the communications systems work in Star Wars, and they can, actually, coordinate clocks across the galaxy with the clocks in the Senate Hall or the Imperial-slash-Chancellor's Palace on Coruscant. They do, since any place that's not on the surface of a planet uses that timezone of that planet as a standard.
  • The use of "universal time" is complained about in one of the X-Wing Series books, when one pilot (an escaped prisoner) realized he's stranded on a planet that's so idiotically in thrall to the Empire as to set its clocks to Coruscant Standard Time. He shortly realizes that he's actually been on Coruscant itself the whole time.
  • In the The Clone Wars, troopers are heard using the term "rotation" to refer to the local day.
  • Justified in the Jedi Academy Trilogy. While on a secret base on the planet Anoth safeguarding the baby Anakin Solo from Imperial kidnapping attempts, Winter insists on setting the clocks to Coruscant time as the base is located in an area where the sky never gets any brighter than twilight.
  • The Han Solo Trilogy: Coruscant provides "Galactic Standard Time" with other planets' days etc. given in its units. However, the local time is also provided. In any case, Han finds it difficult to adjust while on a planet whose day is only ten "standard hours" long (far less than his home world, apparently).
• A Lion on Tharthee addresses this, as the Hexie's planet is 27 hours long, and the resident biologist notes that the human body is only happy with a 24 hour cycle, as women are having irregular menses, while everyone is fatigued and slightly irritable.
• In Rogue Protocol, Murderbot is on a spaceship carrying workers to a colony where they'll work a 20-year contract. When Murderbot asks if that's the years on the planet they're going to, or the calendar years of the corporation that owns their contract, or Corporation Rim Recommended Standard Years or whatever, they've no idea why that might be important.

Live-Action TV

• Star Trek averted it with their stardates, which were totally made-up with no regard to consistency between episodes. This is supposed to be because of differences in time dilation and related Techno Babble at whatever area the ship happens to be at.
  • In Star Trek: The Next Generation, the stardates became more consistent, with the format "4XYZA.B" where number X was the same as the season of the show^note  for example, the first episode of the show is set on Stardate 41153.7 — therefore 1000 stardates would approximate an Earth year. However, this still wasn't quite consistent with passage of time within individual episodes — and also meant that, logically, stardate 0.0 would've had to have been only forty-odd years ago. Later series Star Trek: Deep Space Nine and Star Trek: Voyager kept the same system, meaning the first digit eventually changed over from 4 to 5.
  • On the other hand, certain episodes suggest that while stardates are used for Federation-wide business, member worlds still use their own calendars for local business.
  • Deep Space Nine did slightly avert this trope by also making the station follow the Bajoran calendar, operating on a 26-hour day. (What time zone on Bajor its day corresponds to is never addressed — probably whichever one is the Bajoran equivalent to UTC on Earth.)
  • Sometimes almost explained in the books, stardates generally are based around the rotation of the galaxy, as well as position in it. So depending on velocity (speed AND direction) the stardate could go backwards. All told it's easier just to let it be wrong occasionally.
  • The 2009 film of the series Star Trek retcons the format of stardates again to make it correspond with the Gregorian calendar — thus, Stardate 2258.42 is the 42nd day (i.e. 11 February) of the year A.D. 2258.
  • Klingons use their own dating system, using the life of Kahless as a reference point the way the Gregorian calendar does with Jesus Christ.
• In Doctor Who, the Daleks measure time in "rels". One rel is slightly longer than a second, close enough to do the trick.
  • Doctor Who: The Curse of Fatal Death parodied this with the phrase "Dalek seconds".
• Babylon 5:
  • "By Any Means Necessary" averts this trope as a plot point. G'Kar is worried about losing face because he wasn't able to perform a religious ritual that must be performed at sunrise in front of a specific mountain on a specific day, whether you're actually at the site or not. Sinclair points out to G'Kar that Narn is a little over 10 of their light-years from Babylon 5, meaning that the light that appeared over that mountain 10 Narn years ago will be reaching the station soon. G'Kar uses this loophole to perform the ritual for his people on the station.
  • In "The Hour of the Wolf", Londo makes a Video Phone call to Vir from Centauri Prime. Poor Vir was asleep and wasn't supposed to get up for another six hours; Londo apologizes for forgetting the time difference.
  • References to "sunrise" on a space station in "Day of the Dead" make no sense... unless, perhaps, Babylon 5 is in a synchronous orbit, and they really mean SURFACE sunrise. (The station has sometimes been shown in Establishing Shots moving into the shadow of Epsilon Eridani III and having additional exterior lights turn on.) It's also possible given the content of the episode that it refers to sunrise on the Brakiri homeworld, though we're still left with the coincidence that said day lines up exactly with the station's official day and night.
• In Firefly, River points out that the use of "day" as a time measurement is obsolete, as they are part of a spacefaring civilization spread across hundreds of worlds. This is largely because she didn't get Simon anything for his birthday. Still, her view, like most of her views, appears to be unusual since everybody else celebrates Simon's birthday with no question (well, until the ship malfunctions and nearly kills everybody). Apparently, Earth time is still used for simplicity's sake.
  • Mal walks into Inara's room as they approach a planet and she says good evening. Mal corrects her that it's morning as the time will be 10am at their landing site.
• Played with in Farscape. Rather than use Earth time measurements, they use space equivalents- an "arn" is an hour, a "microt" is a second, and (once or twice) a week is referred to as a "weeken". However, on many occasion someone will mention a length of time known as a "Solar Day"- which is supposed to be one day. This may seem odd considering nobody on the show (short of the main character) has ever even heard of Earth and the term "Solar" refers to Earth's sun, Sol.
  • Not so weird when you remember that in the first episode it is explained that Crichton's been implanted with a Universal Translator which makes him understand all of the alien languages in his own native tongue. Meaning that if Solar is the best translation of the concept in English, Solar is exactly what Crichton will hear.
• The original Battlestar Galactica did much the same thing. The most well-known example of that was the "yahren" or year-equivalent, but there were several others that served as counterparts to seconds, minutes, hours, weeks, etc (though a day seemed to be a day regardless). Unfortunately, the writers seemed to get confused as to what Colonial Unit meant what, which led to it being hard to tell if "microns" and "centons" were units of time or units of length. Fans have tried to get round this by saying that it was common practice to refer to a "light-micron" as just a micron, but actual series canon gives no support for this.
  • Not helped by the fact that a micron is a real unit of length, being a common shorthand for "micrometre".

Tabletop Games

• Averted in Warhammer 40,000, where a universal dating system based on an Earth year is used by the Administratum, but it is purely for administrative purposes and individual planets generally adhere to their own calendars.
  • It's one of very few dating systems with a built-in tolerance for the difficulties and delays of interstellar communication. The first digit of the date specifies the accuracy compared to Earth. a 0 (or a 1) indicates a date on Earth or within the Sol system, a 2 indicates a date somewhere in direct contact with Earth, a 3 indicates a date in direct contact with somewhere in direct contact with Earth and so on. 6, 7 and 8 are used for when the event happened during a period where the place it occurred was out of contact, with increasing degrees of inaccuracy. 9 means the date is wholly conjectural (based on carbon dating, or derived by inference from legends) or converted from a non-standard date system.
  • Mentioned several times in the fluff, particularly Gaunt's Ghosts and the Ciaphas Cain (HERO OF THE IMPERIUM) series, where regiments will adjust their clocks and routines to that of the planet they're travelling to as soon as they board a troopship.
    • The novel The Traitor's Hand takes place on a planet that is tidally locked to its star. It's noted that this makes it almost unique in the Imperium in using the same time everywhere on the planet.
• BattleTech uses earth-standard days, months, and years, calibrated to Greenwich Mean Time. It is noted that planets have wildly different days and years, but interstellar society uses the standard 24-hour day and 365-day year as a convenience to keep interstellar empires together.
• Equinox: Played straight and subverted. A standard Consortium day is 24 hours, but a standard Consortium year is 336 days long (12 months of 28 days).
• In the Three Galaxies sub-setting of Rifts this is a teaser that humans in the setting may have come from Earth, either that dimension's version or another, based on the fact that Galactic Trade Tongue Four, which is used mainly by humans, defines a day as 24 hours long and a year as 365 days, with an extra day every four years. Oh, it is also basically English.

Video Games

• Averted in Dead Space. The opening of the second game is a flashback wherein Nicole called Isaac over video phone, and woke him up because he was asleep. Nicole even explicitly mentioned that she forgot about the time difference between them.
• Briefly seen but never explored in FreeSpace 2. When serving on a Terran vessel, all times are given in the familiar GST format, but on Vasudan ships, Vasudan time is used, which leads to a certain incident being described as occurring at "68:32 Vasudan Standard Time."
• Mass Effect appears to play this straight. The second game takes place two years after the first - this figure is given by any character regardless of species or what world he or she is on. This might be partially a result of the universal aural translator's translation.
  • Explained in the Expanded Universe; the Council created a separate arbitrary Galactic Standard time for the galaxy that isn't based on any single planet specifically to coordinate everyone. And as mentioned above in the tie-in novels, most species' homeworlds have years of similar length to Earth's due to the limitations of main sequence stars' Goldilocks Zones.
    • And the Standard time is not exactly, but close enough to human time that people use them interchangeably. Alternatively, as Shepard has been in the military for years, it's quite possible the references to years are actually to the Galactic Standard and not Earth years. The game offers all three possibilities, but never gives a definitive answer.
    • It may also simply be convenience or even Translation Convention (everyone is either speaking their own language translated into English by tech or Galactic). When Liara tells you that she has been mourning for two years, for example, she may simply be converting her Asari time into Earth time for the sake of politeness, or the Translation Convention renders "I have been mourning you for seventeen zlargs" (or whatever Asari call years/months) as "two years."
  • Averted elsewhere. Each selectable planet has a description, and none of them has anything approaching an Earth day/year.
  • Averted in the case of an advertisement on the Citadel's Zakaera Ward - it gives a date in human time (because the advertisement recognizes Shepard as a human) but in such as way as to make plain that there is a wide variety of galactic time and date systems:
    Advertisement: This is a public notice that Citadel Security will be holding an auction of confiscated property in this Ward on: [*pause, followed by obviously separate recording] Earthdate: August 4 2185 at 08:30 Zulu time. Items to be sold include jewelry, personal electronics, private starships, cargo and sport related personal shuttles, art and antiques from various cultures. For more information visit any C-Sec kiosk, or link into CitadelNet at keywords: C-Sec, auctions, Zakaera.
  • Mass Effect: Andromeda Lampshades it when Jaal is asked how old he is, and he snarkily replies "27 arbitrary years... depends on which planet I'm on."
• An interesting variation occurs in Super Robot Wars Judgment, where the Lunar Furies apparently measure time in galactic days, i.e. the time it takes the entire Milky Way to complete one full rotation. One of their days is roughly several million of our years.
• Justified in the X universe, which features not only interstellar travel but individual ships undergoing time compression. Instead of seconds and minutes, time is measured in sezuras and mizuras or Universal Coordinated Time, values measured from observations of a specific pulsar, and the synchronized 'now' a habit created by the Portal Network trade lanes.
• Averted in Halo: Reach. People paying attention to the cutscenes will note that the time listed in the corner goes past 24 hours. Reach has a longer day than Earth does, although the UNSC still utilizes Earth-time (which does make some sense).
• Played mostly straight in Star Control II, where all dates are kept by Earth time (even the main character's ship, when he wasn't even born on Earth!), and aliens provide you with timespans in human measurements. Some dialogue suggests that the aliens are doing this consciously for the player's benefit, and it is averted by the Slylandro, a race of long-lived gas-giant dwellers who have their own timekeeping system based on their homeworld's rotation. Details here
• Averted in No Man's Sky. Where each "day" varies in length depending the planet you are on. In game each cycle is called a sol and currently there is no universal time measuring unit.
• In Stellaris, every civilization in the galaxy uses the same Gregorian-style twelve-month calendar, with the start date always being 2200/01/01, though it's abstracted slightly in that every month is exactly thirty days (passing as thirty seconds of real time).

Webcomics

• In Darths & Droids, Qui-Gon Jin finally dies by rolling a 1 to stabilize. The DM tries to explain that he can use Fate Manipulation to reroll, since a day had passed. But, being two nerds, Obi-Wan and Qui-Gon talk him out of it be arguing that what is a day since they spent the "night" in space. Is 24 hours a day on Naboo? Or what? Of course, the DM then just says, screw it, you died. At which point they are both happy they won the argument... then realize the prize.
• Starslip averts this when the main character declares he sets his clock by whichever star he's closest to, which in real life would actually be pretty difficult ("I'm late for my appointment at 6! Thousand!").
• Unity uses its own ship-local time, based on sec, kaysec (1000 secs), deci (10 kaysecs), day (10 decis), dec (5 days), and round (5 decs). They also consider a tenround (10 rounds) as a standard-ish unit of temporal demarcation. The actual calendar is just a decimal count (1.000 = 1 day) based on some arbitrary time period without any in-ship time zones, as relative intervals are more important than absolute points in time. Absolutely no attempt is made at dealing with external time references, but without any FTL travel or communication, there's no need for it either. And, the day of the dec is simply the current day value modulo 5; the days are, thus, called "onesday," "twosday," "threesday," "foursday," and "fivesday."
• Schlock Mercenary: The Sol system is standardized to the TTR system, or "terra tempus regula," which is a bad translatineration of "Earth standard time." It's mentioned to be handy enough that everyone uses it, but annoying enough that everyone complains about it.

Web Original

• In Orion's Arm people have given up on trying to establish any such system, even with the help of wormholes.

Western Animation

• Transformers in general plays around with the wording. Whether or not they follow Earth's calendar and time standards is never really expressed, but they use phrases like "One Solar Cycle" to represent 1 day or a Mega Cycle to represent a month (or possibly a year.)
  • The comic books talk about vorns and such, and they add up to a sufficiently random number of Earth years. However, the result is, if you didn't write down how long each unit of time was last time it was told, having no idea how long they're talking about when breems and vorns and joors and such come up.

Real Life

• Truth in Television, the length of solar day (sunrise to sunrise) changes depending on your present location and the time of year. Though the abstract "day" is still 24 hours wherever you go.
  • Antarctic bases tend to use the time zone of the places their supply flights take off from. So some of them use daylight saving during the months in which the sun never sets. And the perhaps-aptly-named "Troll Research Station" tracks Oslo time - meaning that it observes daylight saving time during local winter.
• GPS satellites are basically just clocks, but they are so precise that they have to compensate for both the effects of Special (due to the satellite's velocity around the Earth in orbit) and General Relativity (because the Earth is deeper in a gravity well than the satellites).
• The Darian calendar is a proposed calendar for Mars. It has already attracted controversy from various religious authorities; dates on the calendar occur on the same day of the week year after year because 27-day months skip from Friday to Sunday at the end of the month. This, however, means that the Abrahamic day of rest migrates around the week instead, interfering with the work week.
  • When working with remote landers on the Martian surface, especially those powered by solar collectors, NASA has a vested interest in knowing whether the sun is up or not. Mars missions, therefore, operate on a series of "Sols", which is their shorthand name for the Martial solar day. Some of the folks working on these missions even wear wristwatches calibrated in Martian time, often set for the local "time zone" on Mars where the lander currently is.
• Nobody has developed a calendar for Venus yet, due to its unusually long day compared with its year. However, one possible method of colonizing Venus would be using floating cities that would ride winds that circle the planet every 4 days. This would make it more plausible for colonists to use Earth-length days, with the Venusian year (~224 Earth days) conveniently divided into 8 months of 28 days each.
• UTC is used for various purposes where worldwide uniformity is more important than matching the local time zone. It is essentially a more precisely defined substitute for Greenwich Mean Time, which was previously used for such purposes (and is still referenced in less formal usage as more or less equivalent to UTC).
• Multinational teams on big corporations often resort to use the timezone where their team/project/division manager lives. If the project manager lives in New York, everybody will use US Eastern Time regardless of whether they live in US Pacific Time, Brazil, Germany, China, India or Australia.
• MMORPG guilds and eSports teams with members in multiple time zones commonly use "server time" to schedule raids, rated battlegrounds, practice, events, and anything else. Server time in this instance is the time displayed by the server, which is based on the location of the server.

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