It’s That Time: Atomic Clocks to Add Second

The fact won’t be noted by anyone except the most avid clock watcher, but the world is going to get a little more time this year, authorities said.

At the end of the official calendar day on June 30, the government’s timekeepers are going to add what is called a “leap second.” That means the last minute of the last hour of the last day of June will be 61 seconds long.

The international scientific community will go along with the addition so the world’s time will be standardized.

The need for the additional second, the National Bureau of Standards said, is so “clock time” is the same as “solar time.” The latter is based on the earth’s rotation.

The nation’s scientific time is kept by atomic clocks at the Bureau of Standards and the U.S. Naval Observatory. The clocks are accurate to within one-billionth of a second a day.

The trouble is that the earth’s rotation is not precise. Sometimes the speed increases. More often it decreases.

This means that the two times slowly drift apart, necessitating the change in the atomic clocks.

Leap seconds were first added in 1972, with two inserted that year. Since then, a leap second has been inserted every year except 1980 and 1984. The last leap second was inserted in June, 1983.