From :
http://news.yahoo.com/s/space/20081226/sc_space/2009toarrivenotasecondtoosoon
http://news.yahoo.com/s/space/20081226/sc_space/2009toarrivenotasecondtoosoon
Wait a second. The start of next year will be delayed by circumstances beyond everyone's control. Time will stand still for one second on New Year's Eve, as we ring in the New Year on that Wednesday night. As a result, you'll have an extra second to celebrate because a "Leap Second" will be added to 2008 to let a lagging Earth catch up to super-accurate clocks.
By international agreement, the world's timekeepers, in order to keep their official atomic clocks in step with the world's irregular but gradually slowing rotation, have decreed that a Leap Second be inserted between 2008 and 2009.