An extra second will be added to the world’s clocks at the end of this year, the US Naval Observatory has announced. On December 31, a “leap second” will be added to the world’s clocks at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC). This corresponds to 6:59:59 pm Eastern Standard Time, when the extra second will be inserted at the U.S. Naval Observatory’s Master Clock Fac