The Sumerians of Mesopotamia, who is thought to have invented writing in the 4th century BC, based their numerical system on powers of 60 (instead of 100) subdivided into multiples of 10. It was from this system that Sumero-Babylonians developed the time system that we use today: each hour divided into 60 minutes, which are divided into 60 seconds.
By the way, there are 31 556 926 seconds in a year and 31 622 400 seconds in a leap year.
In olden days time was told mostly by sundials. The first timepiece was a clepsydra, a water clock, introduced at about 1500 BC. Time was measured by the regulated flow of water. Later developments of the clepsydra would drop a metal ball into a bowl upon the hour.
The world’s oldest working clock (pictured) was built in 1386 and is still ticking away at Salisbury Cathedral, UK. Like all clocks of that time it has no face but strikes the hour on a bell.
Today, the International Atomic Time, kept by 300 atomic clocks around the world, keeps earth’s time to within microseconds of accuracy of solar time. However, since the rotation of earth is slightly irregular and slowing down slowly, a leap second has to be added occasionally, giving us the world standard time known as Coordinated Universal Time (UTC).
If all of the above left you scared, you probably suffer from chronophobia, the phobia of time. If you don’t mind the time but suffer from chronomentrophobia, the fear of clocks, head out to Las Vegas: there are no clocks in the gambling casinos.