FreeTime

tool to sync the system clock with the US atomic clock

FreeTime 1.2 is a free utility for Macintosh which will set your system clock to within one-half of one second of exact universal time.

Unlike similar programs, FreeTime obtains its data over the Internet directly from the US Government, and does not require a long distance telephone call. FreeTime also features basic functions to determine your system clock's overall accuracy.