Physical Time

Why We Still Use 60 and 24

Before clocks, humans used the only two reliable cycles in nature: the day (sun) and the month (moon).

• Egyptians (c. 1500 BCE): The first to break the day into smaller parts. Using star patterns (decans), they divided the night into 12 sections and, later, the day into 10 hours plus twilight hours. This gave them a 24-hour day—though the hours varied in length with the seasons.
• Chinese & Indians: Used water clocks (clepsydras) and incense sticks with knots or smells to mark equal intervals. The Chinese divided the day into 12 double-hours, linked to their zodiac.
• Europeans (Medieval): Inherited the systems of Rome and Greece, who used sundials and water clocks but often divided daylight into just 12 “temporary hours.”

The Babylonian Base-60

Around 2000 BCE, in modern-day Iraq, the Sumerians and later Babylonians didn’t count on their fingers (10) but on the knuckles of their fingers (12 on one hand, multiplied by 5 fingers on the other = 60). Their entire math system was sexagesimal (base-60).

This was because it is a superior highly composite number—it can be evenly divided by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60.

60 can be easily divided into 3, but 10 cannot.

The Babylonians applied this to astronomy. They divided the circle into 360 degrees (6 × 60) and the hour (inherited from Egypt) into 60 minutes, and each minute into 60 seconds.

Decimal Time

During the French Revolution (1793-95), France introduced decimal time: 10 hours per day, 100 minutes per hour, 100 seconds per minute.

Clocks were built with 10 numbered faces. It was logical, clean, and purely metric.

It failed because of:

1. Cultural inertia. By the time of the French Revolution, over 4,000 years of astronomy, navigation, and daily life were built on base-60. Every star chart, every ship’s log, every prayer schedule used 24 hours and 60 minutes
2. Practical divisibility. A 10-hour day is elegant but rigid. A 24-hour day can be split in half (12 hours), in thirds (8 hours), in quarters (6 hours), or in sixths (4 hours). These match natural human rhythms (work, rest, sleep) better than decimal’s rigid 5-hour halves or 2.5-hour quarters
3. Navigation & geometry. Maps and compasses still use degrees (360). Converting a decimal hour into a degree for longitude calculation would be a nightmare. 1 hour = 15 degrees is simple; 1 decimal hour = 36 degrees is not

Ancient cultures didn’t settle on the Babylonian system because it was “better” in a modern, metric sense. They settled on it because 60 is mathematically generous. It offers more ways to divide the day into whole numbers than 10 ever could. The Egyptians gave us the 24-hour day, but the Babylonians gave us the gears inside that day.

The French Revolution tried to force logic onto time. But time, like the cultures that measured it, prefers the practical and the inherited over the merely rational. So next time you wait “half a minute,” thank a Sumerian scribe looking at the stars 4,000 years ago. They chose a number that worked beautifully for them—and it still works for us.