This year will be one second longer than 2014. 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.
“The real simple explanation is the Earth is slowing down a little bit,” Nick Stamatakos, the head of the Earth Orientate Parameters at the US Naval Observatory told the Australian Broadcasting Corporation.