…To make the world’s official time agree with where the Earth actually is in space, scientists in 1972 started adding an extra “leap second” on the last day of the year.
For 28 years, scientists repeated the procedure. But in 1999, they discovered the Earth was no longer lagging behind.
The leap second was an unexpected consequence of the 1955 invention of the atomic clock, which use the electromagnetic radiation emanated by Cesium atoms to measure time. It is extremely reliable.
I can save all that time I usually spend entering extra seconds into all the clocks!