This post was most recently updated on December 11th, 2018
The time is shown by default in the Notification area of the Taskbar. The accuracy of the time displayed is determined by time servers that Windows connects to automatically, if your computer is online when the scheduled synchronization time arrives. The two default time servers XP uses are time.windows.com and time.nist.gov. To add additional time servers to the list of choices:
[Start] [Run] [Regedit]
Registry Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DateTime\Servers
Modify/Create the Value Data Type(s) and Value Name(s) as detailed below.
Add a new String Value, assigning it the next sequential number available.
Enter the name of the time server as the data value.
Exit registry and reboot.