LGPSTime

LGPSTime will automatically set your PC clock to the time from the GPS receiver connected to the computer. GPS gets its time from GPS satellites, which are controlled and maintained by the US Naval Observatory. Using time from a GPS, LGPSTime will keep your computer referenced to an atomic time standard. LGPSTime can be launched as a usual application or quietly in the background. A small icon is placed in the tray bar indicating that LGPSTime is running.

Limitations:

14-day trial