Leap second helps us with the reality of time

leap second

To add a leap second on June 30, the official time will be 23:59:60 or 11:59:60 p.m.

Twid/Wikimedia Commons (Public Domain)

Not enough time in your day?

Today, everyone gets an extra second. The Earth’s rotation has slowed down enough to warrant a leap second at the end of June 30. For that second, the official time will be 11:59:60 p.m.

Leap seconds resync human definitions of time with reality. Officially, one day spans exactly 86,400 seconds. Nature, however, is not so cooperative. Earth takes 2 milliseconds longer to complete one rotation on its axis than it did when the day was defined in 1820. As a result, the International Earth Rotation and Reference Systems Service occasionally inserts a leap second at the end of June or December. The world was last granted an extra second on June 30, 2012. 

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

More Stories from Science News on Earth