NetTime

If the accuracy of your system time is of the essence for you or your work, you may want to try a free, open-source, and simple utility like NetTime.

This tiny tool works in the background connecting with remote servers and using the Simple Network Time Protocol (SNTP) to update your system’s clock down to the millisecond.

NetTime is small and works with a minimal amount of system resources. Actually, as you can schedule the update interval, the program will use zero resources while sleeping in the background, and will use up a negligible amount whenever it wakes up to ask for the time to the selected server (typically, every 12 or 24 hours).

The program will not only update your system time whenever an inconsistence is found, but it will tell you the offset and the lag values between your system’s time and the response given by the server in question. To avoid communication errors with the server whenever the time comes to synchronize your system time again, the program works with a small list of them. This also helps NetTime to double-check with more than one server whenever the time returned differs greatly from the time expected.

All you have to do is make sure that your firewall (or any other firewalls on the way) is not blocking NetTime and that the UDP port 123 is free and clear and you won’t have to worry about the accuracy of your computer’s clock never again.