The time keeping system I've been taught and use has the following (cumbersome) units:

Months, Days of the month, hours of the day, minutes of the hour, and seconds of the minute... above and below these units base 10 units are used (e.g. years and milliseconds)

I realize that the awkward calendar units are intended to align the year with the seasons, and the irregular clock units were "designed" for the convenience of dividing the hour (e.g. 1/2 hour, 1/4 hour, 1/5 hour, 1/6 hour) but these days it would seem that a reasonable approach would be Metric Time (e.g. base 10 for all units)...

Is/was any such system ever proposed... or in use? If so, how does it work?

  • 3
    $\begingroup$ The metric unit of time is the second. You can then have kilosecond, megasecond, milisecond, microsecond, and so on. (Some science fiction, set elsewhere than on Earth, indeed does use kilosecond and megasecond in order to sound exotic, I guess.) $\endgroup$ Commented May 31, 2016 at 17:37
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    $\begingroup$ There is also the French Revolutionary Calendar en.wikipedia.org/wiki/French_Republican_Calendar with 10 days per week. It lasted for only 12 years before France returned to the old calendar. $\endgroup$ Commented May 31, 2016 at 17:40
  • $\begingroup$ I suppose that this qualifies as "metric time" - but my thought was could we divide a year into base 10 sub-units that end up replacing the month, day, hour, minute, and second... (we'd lose the astronomical / diurnal relationship in the process - but once we're off of the Earth we're going to lose our Earth biased view of time) - @ Gerald Edgar 2: your link brought this to my attention: en.wikipedia.org/wiki/Decimal_time $\endgroup$
    – Neoheurist
    Commented May 31, 2016 at 17:42
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    $\begingroup$ mentalfloss.com/article/32127/… $\endgroup$ Commented May 31, 2016 at 19:28

2 Answers 2


The French Revolution introduced a decimal clock, where the day was divided into 10 "hours" each, these hours into 100 minutes, and these minutes into 100 seconds. The clock looked like this:


  • $\begingroup$ The pictures of the clocks that you link suggest that I was wrong, and our 24-hour period "day+night" was divided into 10 hours. I edited my message. $\endgroup$ Commented Jun 2, 2016 at 5:47
  • $\begingroup$ You are right. I have changed the answer back to the original formulation. $\endgroup$
    – fdb
    Commented Jun 2, 2016 at 8:49
  • $\begingroup$ They also divided the month into three weeks of ten days. This resulted in three weekends per months instead of four, so the whole thing very quickly became quite unpopular. $\endgroup$
    – user2255
    Commented Jun 2, 2016 at 22:59

EDITED. To add some more information to fdb's answer. They divided the day+night period into 10 hours, so their hour was more than 2 of our hours. They also introduced decimal units for angles (which is closely related to time). 100 decimal degrees in the right angle, so all circumference makes 400 degrees. Every decimal degree is divided in 100 decimal minutes. So one decimal minute is 1/40000 of the circle, and this explains the original meaning of the kilometer: it is one decimal minute, similar to nautical mile which is one usual minute of the Earth circumference. Clocks, watches and angle measuring devices made in that period can be sometimes seen on e-bay.

  • $\begingroup$ Many calculators allow choice of measuring angles in: degrees, radians, or grads. 100 grads is a right angle. $\endgroup$ Commented Jun 3, 2016 at 12:38

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