# Why is the day broken into 24 hours?

Asked by AstroChuck (37664) June 27th, 2008 from iPhone

And who decided on 24 in the first place? Also, why break it up further into 12 in the AM and 12 in the PM?

Observing members: 0 Composing members: 0

The day is 24 hours long because that is approximately how long it takes for the Earth to rotate fully.

If you mean why is an hour the amount of time they decided to use, that I have no answer for because time is a totally arbitrary construct. I imagine that time was in use before people discovered that the Earth rotated the way it does, because otherwise we’d have no leap year (which is a byproduct of our system of time not being exact enough)

jballou (2128)

basically, 24 is nice because it is divisible by 2, 3, 4, 5, 6, 8, 12

AlexChoi (305)

I think the better question is why 7 day weeks? I was unemployed for a couple months and realized that the whole Monday thru Friday, with 2 days off, makes no sense. Days and months are completely made up to keep us from falling out of the bill cycle, keeping us enslaved to some degree. The only real thing is seasons.

SquirrelEStuff (10007)

Okay, jballou. If it makes you happy then let me rephrase it. Why is the day broken into 24 “hours”?

AstroChuck (37664)

@chris6137 so the days and months are keeping us down? Damn those days and months!

AlexChoi (305)

My father explained it once as being a divisible of the circular (360°) rotation of the Earth. It was part of a much longer explanation of the natural balance of 6-cylinder engines, but I was a teenager, and was distracted by thinking about girls at the time.
Also, he was a mathematical genius, and I, to say the least, ain’t.

Knotmyday (7516)

@chris6137
Just guessing, but I would assume we owe the 7 day week to the 6+1 days of creation in Genesis.

Harp (19179)

Oops. Nope, looks like it was Babylonian in origin, derived from dividing the 30 day lunar cycle into 4 parts (they just ignored the 2 extra days).

Harp (19179)

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