# Why are there 24 hours in a day?
**URL:** https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921
**Category:** Factual Questions
**Created:** [August 28, 2004, 6:41am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921 "2004-08-28T06:41:10Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@legion](https://boards.straightdope.com/u/legion)
#### Post date: [August 28, 2004, 6:41am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/1 "2004-08-28T06:41:10Z")
Who decided that a day should have 24 hours and why did this become universally accepted?
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### Author:  [@Walloon](https://boards.straightdope.com/u/Walloon)
#### Post date: [August 28, 2004, 8:06am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/2 "2004-08-28T08:06:10Z")
The Babylonians used 360 degrees in a circle, twelve months in a year, seven days in a week, and twenty-four hours in a day.
[Why are there 24 hours in a day?](http://james.lab6.com/2003/09/16/24hours/)
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### Author:  [@CC](https://boards.straightdope.com/u/CC)
#### Post date: [August 28, 2004, 3:31pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/3 "2004-08-28T15:31:01Z")
Because if there were only, say, 20 hours in a day, we wouldn’t get everything done. Especially those people who work at night. It’s so obvious.
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### Author:  [@toadspittle](https://boards.straightdope.com/u/toadspittle)
#### Post date: [August 28, 2004, 3:50pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/4 "2004-08-28T15:50:08Z")
> [@Walloon](#):
>
> The Babylonians used 360 degrees in a circle, twelve months in a year, seven days in a week, and twenty-four hours in a day.
>
> [Why are there 24 hours in a day?](http://james.lab6.com/2003/09/16/24hours/)
Unfortunately, that site exhaustively explains that it remains unknown WHY a 24-hour day was chosen.
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### Author:  [@akennett](https://boards.straightdope.com/u/akennett)
#### Post date: [August 28, 2004, 4:13pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/5 "2004-08-28T16:13:57Z")
I thought it had something to do with there being 24 beers in a case, but somehow I think that the hours/day ratio was around before the beers/case one.
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### Author:  [@rjk](https://boards.straightdope.com/u/rjk)
#### Post date: [August 28, 2004, 4:22pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/6 "2004-08-28T16:22:24Z")
WAG: The Babylonians liked dozens (twelve months of course, and 360 degrees is an easy multiple), so they went for a dozen hours of light and another dozen of dark.
Lots of old civilizations worked mostly in dozens or scores for convenient groups; we still have a few remnants of those (eggs and beer, “four score and seven”), even though we mostly work in tens.
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### Author:  [@Just1Lurk](https://boards.straightdope.com/u/Just1Lurk)
#### Post date: [August 28, 2004, 4:46pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/7 "2004-08-28T16:46:13Z")
Another WAG: The first chronometers were sundials, divided into twelve (as previously mentioned, because the ancients \*liked \* twelve). They, of course, only worked during the day. When all-day clocks were invented in the middle ages, the clock face was intentionally patterned after the already established sundial.
BTW, this is why clockwise \*is \* clockwise - it mimics the movement of the shadow on the sundial.
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### Author:  [@Fish](https://boards.straightdope.com/u/Fish)
#### Post date: [August 28, 2004, 6:56pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/8 "2004-08-28T18:56:31Z")
> [@Just1Lurk](#):
>
> BTW, this is why clockwise \*is \* clockwise - it mimics the movement of the shadow on the sundial.
In the northern hemisphere, anyway. As everybody knows, in the southern hemisphere, the sun flushes down the toilet the other way round.
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### Author:  [@Corixidae](https://boards.straightdope.com/u/Corixidae)
#### Post date: [August 28, 2004, 7:52pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/9 "2004-08-28T19:52:00Z")
Cecil’s take on this, from way back in 1981:
[http://www.straightdope.com/classics/a1\_125.html](http://www.straightdope.com/classics/a1_125.html)
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [August 28, 2004, 8:27pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/10 "2004-08-28T20:27:04Z")
> [@rjk](#):
>
> Lots of old civilizations worked mostly in dozens or scores for convenient groups; we still have a few remnants of those (eggs and beer, “four score and seven”), even though we mostly work in tens.
A “score” is 20. :smack:
I agree with the rest of what you said though.
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### Author:  [@Agent\_Cooper](https://boards.straightdope.com/u/Agent_Cooper)
#### Post date: [August 28, 2004, 9:49pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/11 "2004-08-28T21:49:44Z")
I’ve read into this before and have yet to find a real answer of why the ancients chose base 12 or base 60. I guess 12 full moons a year makes sense, but idunno. Other theories I have read are far stranger.
I wonder if this is the one thing that everyone in the world just chooses to agree on. Are there any societies that use some other method for counting time? I expect there are small isolated tribes out there who do not know of our way, but have they independently come up with another? There really isn’t anything that makes ours ‘right’. There are countless patterns in lunar/solar cycles that could be used as a basis for a calendar. Do any survive?
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### Author:  [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)
#### Post date: [August 29, 2004, 1:26am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/12 "2004-08-29T01:26:25Z")
> [@Agent Cooper](#):
>
> I guess 12 full moons a year makes sense, but idunno.
Might make sense, but in reality there are 13 full moons in most years.
A full moon occurs about every 4 weeks, so in the 52 weeks of a year there are usually 13 full moons. Not all years, because we’re not working with exact numbers here. For example, in the next 20 years, 17 years have 13 full moons (all but 2006, 2011, 2014, and 2017).
Just one of the oddities of our calendar.
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### Author:  [@Just1Lurk](https://boards.straightdope.com/u/Just1Lurk)
#### Post date: [August 29, 2004, 3:03am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/13 "2004-08-29T03:03:30Z")
> [@](#):
>
> Originally posted by **Agent Cooper:**
> I’ve read into this before and have yet to find a real answer of why the ancients chose base 12 or base 60.
In one of Isaac Asimov’s Black Widower stories, one of the characters advances the theory that 12 or 60 was used for mathmatical convience. Because twelve and multiples of twelve have such a large number of divisors, you minimize the amount of fractions you had to deal with. I mean, have you ever tried to multiply or divide using Roman Numerals?
Counting by twelves was also good news for the merchant; a baker, for example, could sell a half, a third, a fourth, or a sixth of a dozen with no leftovers.
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### Author:  [@hammerbach](https://boards.straightdope.com/u/hammerbach)
#### Post date: [August 29, 2004, 4:23am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/14 "2004-08-29T04:23:03Z")
I believe **Just1Lurk** has it. 12 and 60 are both very divisible. Ten is much less convenient for some things, being evenly divisible only by 10, 1, 5 & 2.
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### Author:  [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)
#### Post date: [August 29, 2004, 1:46pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/15 "2004-08-29T13:46:48Z")
Here’s what I thought was true:
There are 360 degrees in a circle, because it approximated the 365 days in a year (the orbit of the earth being pretty much circular).
The benefit of 360 degrees also being that it is divisible by 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 90, 120, 180, and 360 - which is a hell of a lot of usefulness to work with.
Thus it was decided that the minute is 60 seconds, the hour is 60 minutes, the day is two lots of 12, equalling 24, hours.
The week is 7 days, which upsets that rhythm a bit, but that comes from the year being more accurately closer to 364 days - which is 28 x 13. The moon’s cycle is approximately 28 days, so 13 months (moon-ths) of 28 days fits perfectly into that cycle, and 28 days divide up into 4 x 7 pretty neatly. So it was decided to have seven days in a week.
Of course, 13 is known by many cultures as being a notoriously unlucky number. Plus, there is more than 364 days in a year, so they started to mush things around a bit to sort that out by having 6 months of 30 days, and every alternate month having 31 days, totalling 366. Augustus Caesar’s month had 31 days, so Julius Caesar decided he wanted 31 days in his month too, so now the year had 367 days. Still a bit wrong there, so they took a couple of days out of the end of the year, which in those days was February, and that is why it has 28 days.
When they figured out that 365 is _almost_ correct but _not quite_, they invented leap years and stuck an extra day back into February to occur every four years. And, more recently, to correct that even further they removed the leap year on the turn-of-the-century years except for those that are divisible by 400, which is why 2000 was a leap year but 1900 was not.
I can’t recall who made these decisions and when, but I’m fairly sure I’m mostly right.
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### Author:  [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)
#### Post date: [August 29, 2004, 9:26pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/16 "2004-08-29T21:26:54Z")
> [@rjk](#):
>
> Lots of old civilizations worked mostly in dozens or scores for convenient groups; we still have a few remnants of those (eggs and beer, “four score and seven”), even though we mostly work in tens.
Assuming your were refering to six packs and 12-packs of beer, they are a recent development, relative to “old civilizations”. [This site](http://www.maltshovel.com.au/beerFacts.asp) notes the history of the six pack:
> [@](#):
>
> The first six-pack of beer was produced by the Pabst Brewery in the 1940s. The brewery conducted numerous studies, which found six cans were the ideal weight for the average housewife to carry home from the store.
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### Author:  [@Rubystreak](https://boards.straightdope.com/u/Rubystreak)
#### Post date: [August 29, 2004, 10:44pm UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/17 "2004-08-29T22:44:36Z")
[There was a fascinating study done at Purdue](http://www.innovations-report.de/html/berichte/biowissenschaften_chemie/bericht-15508.html) regarding the biological basis for the 24 hour day schedule. Cells grow in 12 minute intervals, then rest for 12 minutes, and these reactions are apparently governed by a single protein. Thus, the 24 hour day is not merely a human construct; it appears to be hard-wired in most living organisms on the planet. It can be altered by light cycles and external environmental factors, but overall, it’s just the way life on Earth works.
Of course, there are individuals who seem to operate better on a 27 hour day schedule, and even though I’m one of them, I’m not quite sure what to make of that… 😕
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### Author:  [@Walloon](https://boards.straightdope.com/u/Walloon)
#### Post date: [August 30, 2004, 12:44am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/18 "2004-08-30T00:44:17Z")
> [@GuanoLad](#):
>
> Augustus Caesar’s month had 31 days, so Julius Caesar decided he wanted 31 days in his month too, so now the year had 367 days.
Julius Caesar was the first Caesar. Augustus followed him.
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### Author:  [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)
#### Post date: [August 30, 2004, 1:05am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/19 "2004-08-30T01:05:06Z")
> [@Walloon](#):
>
> Julius Caesar was the first Caesar. Augustus followed him.
Oh well. If that turns out to be my only mistake, I’m doing well.
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### Author:  [@Walloon](https://boards.straightdope.com/u/Walloon)
#### Post date: [August 30, 2004, 1:15am UTC](https://boards.straightdope.com/t/why-are-there-24-hours-in-a-day/261921/20 "2004-08-30T01:15:36Z")
Well, actually, the Julian calendar consisted of cycles of three 365-day years followed by a 366-day leap year.
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