(NBC) — This year just got a little longer.
Timekeepers at the International Earth Rotation and Reference Systems Service have added one second to the calendar.
Scientists say that because the Earth’s rotation is slowing down, “leap” seconds are occasionally added to keep clocks accurate.
At least once every 10 years, a second is added to coordinated universal time in order to bridge the gap between the Earth’s time and the atomic clock, which was created in the 1950s.
The extra second may not seem like much, but it ensures that GPS navigation, computer networks for stock markets, and space flight all stay on track.
The extra second is being added on Dec. 31, about five hours before midnight in the Eastern Standard Time Zone.