New Worlds: Hours and Minutes and Seconds

(This post is part of my Patreon-supported New Worlds series.)

Here in the United States, most of us are preparing to “fall back” — setting our clocks back one hour on Sunday, as daylight saving time comes to an end. But not all of us: Hawaii doesn’t observe DST, nor does Arizona, except the Navajo Nation within Arizona does. Indiana does now, but when I lived there, only part of the state did . . . which got even more interesting when you factored in the way that most of the state is in the Eastern time zone, but the northwestern corner near Chicago is on Central.

Why is time so complicated?

The way we handle time now is the current end-product of centuries, even millennia, of accreted systems. Daylight saving time is a twentieth-century invention, stapled onto the late nineteenth-century invention of time zones, grafted atop the mid-nineteenth-century invention of standard time, built on the early nineteenth-century notion of mean solar time, dependent on the creation of reliable clocks and watches, which all rests atop the concept of “apparent solar time” — the kind of thing you measure with a sundial.

But even that isn’t straightforward. Before you can measure time with a sundial or anything else, you have to settle on some kind of unit to measure it with. Your base unit is the day: the length of time from one sunrise to the next, or one sunset to the next, or one noon to the next. Easy enough to eyeball, but not exactly fine-grained or useful in (literal) daily life. So how do you divide it up?

You divide it into hours, is how. The Egyptians had twelve hours in the night and twelve in the day — but theirs were what we now call seasonal, temporal, or unequal hours, meaning they weren’t of set length. An hour was simply one-twelfth of the night or the day, so they varied with the yearly round. Not a whole lot for people near the equator, but the further north or south you go, the more those variations will grow, and the less useful the concept of “an hour” becomes.

What we use now are instead called equal or equinoctial hours, of set length. (Mostly. Once you get into timekeeping on the level of leap seconds, life gets complicated again.) We have twenty-four of these in the day, whether written as 1-12 a.m. and p.m. or the 24-hour clock, and so instead of 6 a.m. being pegged to sunrise, the clock-measured time of dawn and twilight varies through the year.

Why twenty-four? Why twelve hours of night and twelve of day? The usual answer for this is “blame the Babylonians,” but that doesn’t really answer the question. One theory is that it’s based on the 360-day approximation of the solar year (which is five days off, but close enough for ancient government work); another says it’s based on the angle of an equilateral triangle, six of which will go around a circle. Since the Babylonian counting system was sexagesimal, i.e. base 60, they divided that angle into 60 units, and 6 x 60 gets you 360.

The nice thing about 360 is that it’s divisible by a whole bunch of numbers, meaning you can break it up in all kinds of ways — including 12 and 24. The interesting thing is that East Asia hit upon more or less the same answer, without the Babylonians getting involved: the Chinese shi was equivalent to two of our modern hours, dividing the day into twelve parts instead of twenty-four — again based on the stars. Some credit this choice of number to the twelve moons in a lunar year, or to the twelve-year Jovian orbital cycle.

And you can take more or less the same starting number and group it differently. Beginning in medieval Europe the canonical hours divided the daytime up into units of three modern hours, ringing for prayers at 6 a.m., 9 a.m., noon, and so forth. At night, though, they become more irregular. The six-hour clock of Southeast Asia breaks the day into four quarters of six hours each, with the sixth hour of each block getting its own name — sort of like the a.m./p.m. divide, but with four suffixes instead of two. Ancient Hindu timekeeping was complex and used more than one system, but one of them measured the day as consisting of 60 units of 24 minutes each — those familiar factors of 360 coming back again.

Lest you start to think those numbers are inevitable, though, we do have examples to the contrary. Other Hindu systems take very different approaches. Before the shi came into use in China and also after its introduction, the day was divided into 100 , and the night into ten gēng (literally meaning “watch,” as the watchmen beat drums or gongs to signal the divisions). There have been other attempts to institute fully decimal time, most notably for a short period during the French Revolution.

None of those latter attempts have stuck, however rational the idea might be. But going back to the bases of our timekeeping: if you’re writing about another world, whether it’s a fantasy setting or an alien planet, it might make very good sense to divide time differently. If the solar year is nothing like 360 days long, or the lunar year doesn’t have twelve months in it, or there’s some kind of astronomical phenomenon that lends itself to a different division, you could have a twenty-hour day, or a thirty-hour one, or nice well-organized decimal time.

Tracing down to smaller levels — minutes within an hour; seconds within a minute; or whatever the subdivisions are under other systems of measurement — the story is much the same. Our modern minutes and seconds, sixty of each in the next-higher unit, bear the sexagesimal fingerprints of the Babylonians. But for most people’s purposes for most of human existence, those finer-grained units haven’t really been relevant . . . because we haven’t had reliable ways of measuring them.

Which brings us around to clocks. And for those, tune in next week!

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New Worlds: Hours and Minutes and Seconds — 13 Comments

  1. Pingback: New Worlds: Hours and Minutes and Seconds - Swan Tower

  2. I detest daylight savings time.

    That said, I also dislike not knowing what day midnight falls in.
    And I dislike the notation of 12:00am and 12:00pm, meaning 12 before noon and 12 after noon.

    • you mean at noon, yes? 🙂

      as for what day midnight falls in…do your days start at dusk, dawn, or some other point in time? *is curious*

    • Most people I know turn out to detest the switch between DST and normal time — is that the case for you? Me, I’d be happy if we just went to DST year-round. It depresses me so much when we fall back and suddenly it’s dark so early. But I also know that I’m not a morning person anyway, and I have some sympathy for the people who say it’s harder to wake up in the morning if it isn’t light out yet.

  3. Noon is not before noon nor after noon.

    If I want to tell someone that the party is on midnight of December 1 – does it mean a minute after 11:59 of December 1, or a minute after 11:59 of November 30?

    The old definitions of days starting at sundown are largely forgotten. Instead of Christmas eve meaning the evening of Christmas (starting at sundown) (or Halloween for that matter), it usually means the whole day before. In fact, some people say December 23 is Christmas eve eve.

    So days end and start at midnight. Technically, noon and midnight are 12m and 12mm, but nobody uses those terms. 12am and 12pm are not only irrational – but worse, they are ambiguous.

    • Days starting at sundown is one way of doing it; days starting at sunrise is another, and in practical terms that’s the way I usually see people talking. If I talk about going to bed at 2 a.m. yesterday or last night, everyone is going to assume I mean eleven hours ago (I’m typing this at 1 p.m.), not thirty-five hours ago; by strict technical terms eleven hours ago was today, not yesterday, but that isn’t actually how people mostly talk. If you say “I’ll do it tomorrow” at 11:50 p.m., nobody is going to think you mean that you might do it fifteen minutes later. Socially speaking, the next day begins when the sun rises or you wake up from sleep.

  4. >The old definitions of days starting at sundown are largely forgotten.
    oy vey, they are not.

    and if the party is one that’s held annually, most attendees would already know which day it follows. (in my experience)

    • Yeah, this came up in the original round of time discussion — Jewish tradition still keeps the “starting at sundown” form (though most American Jews, at least, would probably not say “tomorrow” and mean later in that same western calendar day).

  5. Muslim prayer times are not in terms of hours, which makes me think that the timing used in Arabia C. 800 wasn’t, either, and I have seen references to the use of solar time in other cultures, too. I don’t think that the requirement for ‘our’ sort of time is as critical as you imply, though I agree it’s needed as soon as you start scheduled services of any description.

    • I don’t mean to imply that it’s critical — in fact, a future post will be about how differently we relate to time depending on technology and circumstances.

  6. The best time for scheduling is universal (zulu, GMT) time. The same time for everybody. China only has one time zone for that purpose. And when I was a USAF pilot, we partially used that, to avoid confusion.

    My son-in-law one time got an e-mail wanting him to go to a meeting. Microsoft Office converted the time from Pacific Time to Rocky Mountain Time, which makes perfect sense for a phone meeting. But he flew in, and was an hour late.

    • My husband’s company has offices on the East and West Coasts of the U.S., in Poland, and in India. When they’re trying to schedule meetings between people in those different areas, yes, they use GMT. But it’s all about context: I remember growing up watching broadcast TV in Texas and always hearing the ads for shows say “starting at 8 p.m., 7 Central.” For that context, noting it in terms of U.S. time zones is generally more convenient than referencing a standard based in a completely different country. (These days, of course, I watch almost everything streaming, so broadcast times don’t matter. 😛 )