This year, we all get an extra second on June 30

The last minute of June 30, 2015 will have 61 seconds. Scientists have announced that they’ll be adding an extra second, called a “leap second” to the UTC (coordinated universal time) clock on June 30 at 11:59:59. That means the clock will read 11:59:60.

This is because the Earth is moving a little slower than our super-accurate atomic clocks dictate, and it’s getting out of sync. In fact, while atomic time is constant, the Earth’s rotation is slowing down by around two thousandths of a second each day.