Newer Than They Think / Chronology

• Minutes and seconds as we know them were first used near the end of the tenth century. (The names are a clue: minute fraction of an hour, and second minute fraction; "thirds" and "fourths" were once used in calculations, although not measured for obvious reasons.) Before that, the only culture not to use fractions of an hour was the Babylonians, who would divide days by sixtieths, into units of twenty-four minutes, twenty-four seconds, six fifteenths of a second, etc. Seconds could not be measured until the sixteenth century, and nothing resembling our concept of counting time by seconds shows up until late in the seventeenth.
• The AD dating system was not devised until AD 532, and not widely used until the 9th century AD. Before that, Christians often dated from the supposed date of the Creation (5492 BC), the supposed birth of Abraham (2016 BC), and many other epochs.
  • If they dated years that way at all: many just used terms like "the 18th year in the reign of King Whatshisface". (This convention was commonly used in dating British legislation until quite late in the reign of Queen Victoria, and remained part of the official legal citation form until 1963.)
    • Still the case in some countries, e.g. Japan, where official calendars refer to the era name; since 1868 a calendar era coincides with the reign of an emperor, but before then they were shorter, new eras often being declared for recovery from major disasters. The current era (beginning in 2019) is Reiwa, the reign of Emperor Naruhito.
    • Legislation is also still numbered by regnal year in Canada; thus Canadian statutes passed in 2015 are dated to the 64th year of the reign of Elizabeth II. (It's slightly more complicated than that, as statutes are dated to the session of Parliament, which generally spans two calendar years, but that's enough of that now.) They do use the conventional year also.
    • In some regions of Europe historians continued to use AUC or other Roman chronologies ^note For example, the "Spanish Era" in the Iberian Peninsula, which began in 38 BC when the region was declared pacified by Augustus well into the 14th and even 15th centuries. It's ironic that this practice died precisely during The Renaissance.
    • It is also sometimes stated the Ancient Greeks counted the years by the Olympic Games. In reality, this system was only used since the 4th Century BC, and then only by historians. Any official documents used years named after officials, with each state, naturally, having its own calendar.
    • Fun fact: The earliest event which we can date with any certainty is the Battle of Halys (May 28, 585 BC), which was called off due to a solar eclipse (which is how we know it was on May 28th).
• New Year's Day, until a few centuries ago, could fall on a number of different days depending on the country, most commonly March 25th and September 1st. Great Britain didn't move New Year's to January until 1752, concurrent with its adoption of the Gregorian Calendar.
  • Furthermore, New Year's Day wasn't a public holiday in the UK until 1974.
• The concept of decades as a unit of time (and its associated tropes) did not exist before the 20th century, and was really only popularized by the 1931 book Only Yesterday by Frederick Lewis Allen, which retrospectively examined The Roaring '20s. Prior to then, periods of time shorter than a century but longer than a year would be expressed in terms of ages, eras, or periods, but not decades. The word itself could just as easily mean ten days — and in many languages still does.
• The idea of date changing in the midnight was coined only in the 18th century. Before that, sunset was considered to be the time of the change of the date. The sunset as date change is still followed by observant Jews, Muslims, and some Christian sects. For Romans and Greeks, it could start as sunrise. Also, the day and the night were each divided into twelve hours separately, making for different lengths depending on the season.
• The Chinese adopted the twelve hour day only in the 18th century. Before that, they used decimal reckoning. They considered the twelve hour day as a retrograde step.
• Time zones were not invented until the 19th century (and, contrary to a lot of people's understanding, they were invented and not discovered — they are not natural entities, but useful conventions). People understood since antiquity that the local solar time depended on where you were (i.e., that "solar noon" — the point at which the Sun was at its daily zenith — varied by longitude), but standardization of this into "zones" that all shared the same time (only loosely based on the Sun's position) was first done by railroad companies that discovered that every town having their own slightly different time would lead to really bad results when trying to have train schedules or sharing railroad tracks.
• The first recorded instance of someone "losing" a day because of circumnavigation of the Earth was, understandably, a result of Magellan's voyage around the Earth in (1519-1522). Though it makes sense in principle that if the Earth is round and time is dependent on longitude, that you can "gain" or "lose" days depending on which way you go, nobody in human history seems to have anticipated this fact until Magellan's crew experienced it. The crew, which kept assiduous track of the days that had passed in the ship's logbook, was shocked when they arrived in a port where the date was out of sync, and it took some time before scholars worked out what had happened.
• The ability to travel such a great distance that one's Circadian rhythms can get significantly out of sync with local time was not possible until the 1880s, with the development of steamships & the evolution of train technology. Jet-lag was previously known as "boat-lag" until airplanes displaced ship-based trans-oceanic travel in the 1950s.
• The Roman convention of dating years from the founding of Rome in 753BC (which would be AUC 1 under this system) was not a Roman convention at all, but rather, one of Renaissance writers. The Romans did not number years, but rather, identified a year by the names of the two consuls who had served their terms in office that year.

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