When dicussing time zones with a friend the other night, the question came up about the origin of the 24-hour day. I've had the opinion for quite some time that how we decide to measure things like the length of days, weeks, years, etc is rather arbitrary and while the measurment systems that have become practically universal have probably been popular for a reason, it's really just a matter of convenience and who is to say that we couldn't have come up with a different system that would work jst as well or maybe even better?
So, who do we have to thank for hour 24-hour day? (A Wikipedia Study)
According to Wikipedia, the Ancient Egyptians are who we have to thank for the first 12-hour clock; the days were divided with 12 hours from sunrise to sunset and 12 hours from sunset to sunrise (consquently, the length of the hours changed seasonally). Time was told on a sundial for day and a water clock for night.
The Romans also had a 12-hour clock; the days were divided into 12 equal hours (again, length changed throughout the year) and the night was divided into three "watches."
The first mechanical clocks, in the 14th century, had dials that actually showed all 24 hours.
It seems that most countries use 24-hour time notation as opposed to 12-hour, but as far as this dicussion is concerned, they're the same thing. There are a few exceptions:
In Thailand, next to the 12-hour and 24-hour clock system, a 6-hour clock system is also used, especially in spoken language. It counts 4 times from 1 to 6, with different additional words to make the distinction for night, morning, afternoon, and evening. 24 is divisble by 6, however, so it still fits into the same system, no matter how much it is divided up by language.
Apparently some situations in Canada use something called "metric time," but I'm not sure it's exactly what metric time would be. Check out the Wiki article on metric time and this picture of a French Revolutionary decimal clockface.
So, there's plenty of fodder in case I feel like writing a story based around time manipulation, which was a vague idea I had (we change how time is organized, and consequently learn that there was an excellent reason for 24-hour days). The most obvious thing to me, I guess, is that time will continue to pass no matter how we divide it up, and how we divide it up is a matterof convenience. If we were nocturnal animals, perhaps we would have come up with something completely different (sundials would probably not have been the original method of telling time).