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As I understand it, pretty much everybody uses the "Babylonian/sexagesimal" time format: 12/24 hours in a day, 60 minutes in an hour and 60 seconds in a minute.

Have there been alternative systems to accurately tell time? Or maybe there are still some in existence?

By "accurately" I mean that one can tell an exact time, i.e. not the "some time during the morning"-type. Also, let's exclude inventions that were never properly used over a longer period, e.g. decimal time during the French Revolution.

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    $\begingroup$ Would the four-section Thai system of telling time be an answer? Telling minutes and seconds in Thai is as usual. $\endgroup$
    – bytebuster
    Mar 10, 2016 at 10:21
  • $\begingroup$ There's the Swahili clock: google.com/#q=swahili+clock $\endgroup$
    – Yellow Sky
    Mar 10, 2016 at 10:25
  • $\begingroup$ The 12/24 part is not exclusively Babylonian, ancient Egyptians and Chinese also had this division, for different reasons, and independently of Babylonians. hsm.stackexchange.com/questions/2876/… $\endgroup$
    – Conifold
    Mar 11, 2016 at 19:42
  • $\begingroup$ @yellow sky: it would be interesting if you could elaborate a bit more - it seemed to me, that they still used a 24 hour division, though - or did I misunderstand this? $\endgroup$
    – Gerhard
    Mar 11, 2016 at 20:10
  • $\begingroup$ Swahili time is just the 24 hour system but starting at sunrise rather than midnight. There's also the Bohemian time (which is shown on the famous clock in Prague) that starts half an hour after sunset but the hours are the same length as hours, so in autumn the day is slightly shorter than 24 hours and in spring a few minutes longer. But it's still based on the 24h system. $\endgroup$ Dec 3, 2021 at 8:57

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"Swahili time" is essentially the same as contemporary standard time, synchronized at sunrise / sunset (6:00), so it has the same 12/24 system. There is a Chinese time unit the ke, 14.4 minutes, but it apparently co-existed with a duodecimal system so one can suspect that it was added to a duodecimal system, used exclusively (as far as I can determine) with months.

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French Revolutionary time had ten hours to the day, 100 minutes to the hour, and 100 secnds to the minute. That same article describes a couple of other instances of decimal time.

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    $\begingroup$ Thanks, but I had explicitly excluded decimal time during the French Revolution, as this has neither "developed"\is a traditional way of telling time, nor has it been used over a longer period of time. $\endgroup$
    – Gerhard
    Mar 11, 2016 at 19:13
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There is the traditional Chinese timekeeping which uses various units that are not based on splitting the day in 12/24 parts (but other units that do).

It is described in detail in Wikipedia. It is really complicated with a huge bunch of units, partly overlapping in their definition and partly coming from different regions or periods. There are also separate systems for day and night.

No point repeating all the details from Wikipedia, but here are some quotes that are relevant to your question about accuracy about units that go down to milliseconds (!):

Days were also divided into smaller units, called kè (刻). One kè was usually defined as 1⁄100 of a day until 1628, though there were short periods before then where days had 96, 108 or 120 kè.

Using the definition of kè as 1⁄100 of a day, each kè is equal to 0.24 hours, 14.4 minutes, or 14 minutes 24 seconds.

Kè were subdivided into smaller units, called fēn (分). The number of fēn in each kè varied over the centuries, but a fēn was generally defined as 1⁄6000 of a day. Using this definition, one fēn is equal to 14.4 seconds. This also means that a fēn is 1⁄60 of a major kè and 1⁄10 of a minor kè.

In 1280, Guo Shoujing's Shòushí Calendar (授时曆) had each fēn subdivided into 100 miǎo (秒). Using the definition of fēn as 14.4 seconds, each miǎo was 144 milliseconds long.

The Mahāsāṃghika, translated into Chinese as the Móhēsēngzhī Lǜ (Taishō Tripiṭaka 1425) describes several units of time, including shùn or shùnqǐng (瞬頃; 'blink moment') and niàn. According to this text, niàn is the smallest unit of time at 18 milliseconds and a shùn is 360 milliseconds.

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The ancient Israelites divided each of the 24 hours in a day into 1080 halaqim, making each heleq 3⅓ seconds long.

  • 1 part (heleq) = 76 moments (rega'im) (each moment, rega, is 0.04386 of a second; 22.8 rega'im is 1 second)
  • 1 hour (sha'ah) = 1080 parts (halaqim) (each heleq is 3⅓ seconds)
  • 1 day = 24 hours (sha'ah)

Biblical and Talmudic units of measurement - Wikipedia

The rega unit is about 44 milliseconds, or one twenty-fifth of a second. Except perhaps for long time averages in astronomy, I've no idea how or why such precision would be used during those times.

They determined that the average month (new moon to new moon) lasts 29 days, 12 hours, 793 halaqim, which is less than half a second longer than the currently known value.

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  • $\begingroup$ To this day, in synagogues around the world, during the prayer for the new month (on the Sabbath before it begins), its time is announced in terms of day, hour, minutes, and halaqim $\endgroup$ Dec 5, 2021 at 4:36
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It is not clear what you are asking about: clocks (devices to measure time) or systems to record the time. Ancient Babylonians had no clocks. Time recording was needed for astronomy. As true (quantitative) observational astronomy began in Babylon, their time recording system spread universally. Clocks were a later invention (water clocks), and this had little to do with the system of units; the system of units only tells you how to divide the dial. The French, when they introduced a universal decimal system of units for measuring everything during the revolution, tried to introduce it for time and angles as well. This did not work because the Babylonian units of time and angles were already universally accepted.

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  • $\begingroup$ I am interested in alternative "systems". If there are no alternative ones, that is fine for me as an answer, but it is not obvious to me that no one devised a system before or in parallel to the Babylonians - the world was not that globalised at that time. $\endgroup$
    – Gerhard
    Mar 11, 2016 at 19:38
  • $\begingroup$ @Gerhard: some examples of alternative systems of marking time were given in the answers. $\endgroup$ Mar 11, 2016 at 23:00
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The reason a clock uses 12 hours is actually simple: use a compass/forked stick in the sand to make a circle. then, naturally one would place one leg of the compass at some point on the circle, and draw a second circle. then, one would naturally place the leg on one of the intersections just made, and draw a third one. 3 more times, and you have gone all around and drawn a pattern of 1 circle in the middle (the 7th) and 6 circles around.

This means that, division in 6/12 is the easiest, and also most accurate way of dividing a circle in the past. Dividing a circle in 5/10 parts is really hard to do accurate with only the 'euclidian tools'(pencil, ruler, and a pair of compasses).

Note also that a number system based 60 is easy to make calculations with. Imagine a dollar having 60 cents, makes it much easier to share this dollar with 2,3,4,5,6 people. Also note that you can count 60 on your fingers, when counting 12 digits on your one hand, and 5 fingers on the other hand (5x12=60). Doing this, you even do not need one thumb, so you can hold your merchandise while counting :)

Since your question is about accuracy, i need to add that while we think of an hour now as a fixed unit, before the invention of the clock, hours were 'variable' in the sense that a day is shorter in the winter, so while there was a division in 12 parts, the parts were not always equal.

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    $\begingroup$ While your assertion(s) sound interesting, I think it would be appropriate to back them up with some sources. $\endgroup$
    – Danu
    Jun 12, 2016 at 12:57
  • $\begingroup$ to some extent you are just naming the advantages of the duodecimal system in general - that is why e.g. the "dozen" was widely used in the past. When it comes to the circle, however, I would assume that dividing it into e.g. 4/8/16 sections is not harder than into 6 or 12. $\endgroup$
    – Gerhard
    Jun 14, 2016 at 9:39
  • $\begingroup$ @Gerhard I strongly disagree here. Dividing a circle in 4 parts, done accurately, needs 3 extra circles to know for sure that the straight lines that make the divisions are on a 90 degree angle. To divide in 6, you only need to use the same forked stick and 'rollover' it along the first circle. Easy as cutting a pie.. $\endgroup$
    – Erik Goff
    Jun 21, 2016 at 20:22
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    $\begingroup$ Either way, it does not answer the question. $\endgroup$
    – Gerhard
    Jun 21, 2016 at 20:42

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