CentralNotice Leap second From Wikipedia, the free encyclopedia Jump to: navigation , search Screen capture of the UTC clock from time.gov during the UTC leap second, on June 30, 2012, 23:59:60. A leap second is a one- second adjustment that is occasionally applied to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time . Without such a correction, time reckoned by Earth rotation drifts away from atomic time because of irregularities in the Earth's rate of rotation. Since this system of correction was implemented in 1972, 25 such leap seconds have been inserted. The most recent one happened on June 30, 2012 at 23:59:60 UTC. [ 1 ] The UTC time standard, which is widely used for international timekeeping and as the reference for civil time in most countries, uses the international system (SI) definition of the second, based o...