NTP or Network Time Protocol allows atomically synchronised time to be distributed across the Internet using co-operative servers. Chorver's time server time.Chorver.net:123 is synchronised with 3 atomic clocks across the Internet. It also creates a drift file which enables it to understand the accuracy of the servers internal clock and automatically adjust it in between updates.

Unix servers inherently support the NTP protocol, and can be setup to use Chorver's NTP server. See: Linux NTP setup.	Windows requires a third party application to use this feature, one source of which can be downloaded from here.
Mac OS X supports it directly, for details of how to set this feature up visit apple's relevant FAQ here.	For the relevant RFC (Request for Consideration) proposing this service back in 1983 visit RFC 868.

"You may delay, but time will not."
Benjamin Franklin