Who decided -and when- that the day should have 24hs?

Question

and why not 20 ... or 10? and why is one hour made of 60 minutes, and not 100... or 50??

Answer 1

It is 24 hours because that is how many hours it takes the Earth to make one rotation.   Like a top, the Earth spins and takes 24 hours to make one full rotation.  It's actually a hair longer but a leap year evens it out.

Answer 2

24 hrs just for the simply reason that the earth rotate in his ege in that time

Answer 3

10 Hours a day was used as one of the French Revolution reforms on 5 October 1793.

Charles-Gilbert Romme proposed the revision of the calendar.

Answer 4

God

Answer 5

not sure but good question

Answer 6

This is all because of the Babylonians.

The Babylonians loved the number 6 (for reasons we don't really know), and multiples of 6. Ten is a convenient number too -- because we all have 10 fingers -- so 6 x 10, or 60, was especially useful to the Babylonians.

So the forenoon was divided into 6 hours, and the afternoon was divided into 6 hours. And that meant that the evening and wee hours had 6 hours each too. That makes a 24 hour day (6 x 4).

That's also the reason an hour has 60 minutes, because the Babylonians used a base-60 counting system (also called a sexigesimal system). So each hour was divided into "minute" (very small) parts, each minute part being 1/60th of an hour. And each minute was also divided into "second minute" parts which we call seconds.

That's also the reason a circle has 360 degrees. First you divide a circle into 6 parts (the magic number) and each part has 60 minute parts, for 360 degrees all the way around.

When Alexander the Great conquered Babylon, the Greeks picked up the Babylonian system, and when the Romans conquered the Greeks, the Romans picked it up from them. From there it spread throughout Europe and to us.

Answer 7

Whoever invented our current time system must have really liked multiples of 6.