It seems to me that subdivisions of a day are rather arbitrary. When did a minute become a minute, an hour become an hour, etc.? Also, what are some other time-keeping methods?
It is based on the Sexagesimal(Base-60) number system. An hour is 60 minutes for the same reason a complete circle is 360 degrees. Other time-keeping methods; water clock, sundial, hourglass, etc. They don’t necessarily need to correspond to a base-60 time system they can be used simply to judge “the water is half run out that is a long time” or “The shadow is pointing toward the big hill over there that means it will be dark soon”. I recommend A Walk Through Time, a website created to answer this very question.
"Ice-age hunters in Europe over 20,000 years ago scratched lines and gouged holes in sticks and bones, possibly counting the days between phases of the moon. Five thousand years ago, Sumerians in the Tigris-Euphrates valley in today’s Iraq had a calendar that divided the year into 30 day months, divided the day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts (each like 4 of our minutes). We have no written records of Stonehenge, built over 4000 years ago in England, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on. "
An easy read on the subject is Isaac Asimov’s The Clock We Live On.
See http://en.wikipedia.org/wiki/Decimal_time: “French Revolutionary Time, which divides the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal seconds.”
Interesting article!
Don’t forget Time Cube!
This much I do know, although there is more to be said. Originally in western society, the day was divided in 12 equal hours (whose length then varied through the year, depending on your latitude) and 4 equal watches, whose meaning is self-explanatory. Why 12 and 4? I don’t know, but somebody might. Well, I guess the 4 watches were convenient for watchers. The 12 hours may have had something to do with a base 60 but could also have been an early base 12 usage.
Our “noon” was originally the ninth hour (about 3PM) and was originally dinner time. Gradually things changed and standardized the hour and made the day start at midnight instead of sunrise.
Already in ancient times angles were divided into 60 minutes (that is small parts) and I think the Babylonians who used a base 60 numeration did that. So when people came to feel the necessity and had the possibility of breaking the hour into small parts, 60 minutes must have seemed like an adaptation of the system for measuring angles. (This is really pure conjecture on my part, understand.) The next thing I am surer of. When the time and possibility arose of dividing minutes (both angles and time periods) more finely, they adoped “second minutes” and angles and hours had 60 small parts per degree or hour, they chose to divide minutes into 60 second minutes. (Did they originally called minutes “first minutes”? I don’t know.) Of course, in the fullness of time “second minute” got shortened to “second”.