Internet Time Synchronization skill available in XP as it has ability of mechanically synchronize clock on PC with internet time server. But ensure that only two servers are given which is time. Windows.com and time.nist.gov. Ensure that if firewall used, you may include server to access to PC/network. Time Service utilizes post 123 on local system. But also include time server on to system. Internet Time Synchronization permits PC clock to be synchronized with time server on Internet.

In XP freeware atomic clock Synchronization has utilized in that kind of utility you use it and then optimize that windows reference clock server which is usual. Ensure that if dates for Daylight Saving Time (DST) altered newly in area, you should update OS with new rules. Atomic Clock Sync help to fix XP time service if PC is no longer able to check for Internet Time updates. Also edit registry for add time server. Use server like clock.isc.org and 128.105.37.11.