'Leap Second' Will Make New Year's Eve Just a Little Bit Longer

World clocks will officially add a "leap second" at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC), which is the time standard set by highly precise atomic clocks. The extra second of party time is designed to reconcile two ways of keeping time: atomic clocks, and clocks based on the Earth's rotation. "Earth is slowing down over geological time, and that can lead to a problem when you've got a ton of clocks," Demetrios Matsakis, chief scientist at the U.S. Naval Observatory