Hi all -- FTP, so please forgive any incorrect formatting, but this question has been on my mind for years and I never found a good place to ask it until I stumbled onto this sub a few days ago. Thanks in advance!
Given how hard it's been to get the world onto the metric system for distance, weights, and temperature, I'm shocked at how universally we all seem to measure time in the same way. Years, months, and days have "real" phenomena setting them, so I see where those would come from. But what about weeks, hours, minutes, and seconds?
This is taken from https://nrich.maths.org/6070
There are various theories about how the 24 hour day developed. The fact that the day was divided into 12 hours might be because 12 is a factor of 60, and both the Babylonian and Egyptian civilisations recognised a zodiac cycle of 12 constellations. On the other hand, (excuse the pun) finger-counting with base 12 was a possibility. The fingers each have 3 joints, and so counting on the joints gives one 'full hand' of 12.
In classical Greek and Roman times they used twelve hours from sunrise to sunset; but since summer days and winter nights are longer than winter days and summer nights, the lengths of the hours varied throughout the year.
In about 50 BCE Andronikos of Kyrrhestes, built the Tower of Winds in Athens. This was a water clock combined with Sundials positioned in the eight principal wind directions. By then it was the most accurate device built for keeping time.
Hours did not have a fixed length until the Greeks decided they needed such a system for theoretical calculations. Hipparchus proposed dividing the day equally into 24 hours which came to be known as equinoctial hours. They are based on 12 hours of daylight and 12 hours of darkness on the days of the Equinoxes. However, ordinary people continued to use seasonally varying hours for a long time. Only with the advent of mechanical clocks in Europe in the 14th Century, did the system we use today become commonly accepted.