Answer: The Egyptians

Why do we have twenty four hours in a day–as oppose to twenty, or twelve, or any other division of time? To uncover the mystery of the twenty-four hour day we need to take a trip back to ancient Egypt.

While many cultures around the world use a base-10 system (largely in part because they began their exploration of mathematics by counting their ten fingers), ancient Egyptians used a base-12 system. Instead of counting their individual digits, Egyptians instead counted the knuckles of each each finger using their thumbs as pointers (four fingers on each hand, three knuckles per finger, twelve total units).

It was this base-12 system that led the Egyptians to divide the day into 24 hours (two divisions of 12). What’s even more interesting about the Egyptian division of the day is that light and darkness each had their own 12 hours–so in the summer when the daylight hours were extended the 12 hours of the day were longer and the 12 hours of the night were shorter. Individual hours of the day did not have a fixed length until Greek mathematicians proposed such an arrangement in order to facilitate easier calculations. Even then the length of individuals hours remained largely fluid until the advent of mechanical clocks nearly fifteen centuries later.