'Leap Second' to Be Added on New Year's Eve This Year

Leap seconds are a way to make up for this difference. Since 1972, the International Earth Rotation and Reference Systems Service (IERS) — the organization that keeps track of time for the world — has added 26 leap seconds to atomic clocks, with the last such insertion coming on June 30, 2015. "We can easily change the time of an atomic clock, but it is not possible to alter the Earth's rotational speed to match the atomic clocks," officials with the U.S. Naval Observatory (USNO