Leap Second

[David Morris]

http://laughingsquid.com/leap-second-scheduled-for-june-30-2012/

Clock enthusiasts take note: A leap second has been scheduled for June
30, 2012. A leap second is an adjustment to the atomic clock-based
Coordinated Universal Time (UTC) to bring it more closely in line with
Universal Time (UT), which is based on the rotation of the earth. The
two time standards do not agree because the earth’s rotation is ever
so gradually and unpredictably slowing down. Yes, really.