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We can actually thank the Egyptians and Babylonians for the hour, minute and second:
Egypt (around 1300 B.C.E.) measured their daylight, twilight, and darkness. They found the ratio of 10 : 2: 12, thus our 24 hours in a day. No one specific person can be credited for this, it's lost for the ages. But we do know it was the Egyptians. They are also responsible for the 365 days in a year!
Then came the Babylonians (around 200 B.C.E) who used a base-60 counting system for their astrological calculations. It was easy to divide by 2,3,4,5,6, and 10. They are responsible for breaking up the hours into two sexagesimal (base-60) units. The first being minutes, and then seconds.
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