(NBC News) Leap seconds happen occasionally to keep clocks in sync with the slowing of the earth’s rotation and to make sure they are as accurate as possible. This year’s leap second was announced by the international earth rotation and reference systems service, that’s the group responsible for adding leap seconds to international time. The time keepers said, “We can expect the clocks to read 11:59:60 instead of 11:59:59.”
The leap second has the potential to cause chaos for computers that can’t deal with a 61-second minute. The most recent leap second happened just last year, on June 30th.