There’s an additional second being added to tomorrow, New Year’s Eve. The atomic clocks that are used to track time degrade in a stable pattern while the earth’s rotation is not as regular. So, from time to time, an additional second is added on, like this year 2008, in order to reconcile things.
Of course, if you’re running OS X and you’ve got your Mac pulling time from Apple’s time servers (that’s the default setting in the Date & Time preference pane), you’re taken care of. And if you’re on Windows, well, er, we’ll let Microsoft explain:
“The Windows Time service does not indicate the value of the Leap Indicator when the Windows Time service receives a packet that includes a leap second. (The Leap Indicator indicates whether an impending leap second is to be inserted or deleted in the last minute of the current day.) Therefore, after the leap second occurs, the NTP client that is running Windows Time service is one second faster than the actual time. This difference is resolved at the next time synchronization.”
Uh. We think that means you’re fine. But maybe you want to keep a fire extinguisher on hand…just in case.