How can I update the clock on my Windows XP machine? Why does the clock always drift away from the actual time?
The computer clock will gradually get out of line with reality since it's not a very accurate beast. Some software can check the time with an outside source on the network or Internet and regularly adjust your computer by a few seconds so it never drifts so far off that you would notice.
If your computer is a part of a domain (not possible in Home Edition) you do not need to do anything. The computer will automatically update it's time by querying the PDC Emulator (usually the first DC n the domain).
If you still want to adjust your clock (you shouldn't because it might have adverse effects on some of your network connections and management tools) you can run the following command:
net time %logonserver% /set /y
(%logonserver% can be used as a variable, but you can specify a DC name if you want).
If you're not a part of a domain and still want to update your clock automatically, you can right click the clock found on the tray area on the lower right of your screen and choose "adjust time/date".
Click on the Internet Time tab, then select the "Automatically synchronize with an Internet time server" checkbox.
This will work for most people, but what if the only 2 time servers specified in the drop list cannot be reached for various reasons, and you want to synchronize with an alternate time server, perhaps a time server found on your corporate LAN or elsewhere on the Internet?
To do this you have to use the command prompt and even poke around in the registry.
In the command prompt type in the following line:
W32tm /config /syncfromflags:MANUAL/manualpeerlist:
tick.usno.navy.mil and tock.usno.navy.mil and even time.windows.com are examples of public time servers that you can put in the manualpeerlist. These are special computers on the Internet that keep very exact time by various means. Your computer can check time settings against one or more of these computers and gradually adjust accordingly. Normally you list several servers in case one is unavailable at any time.
It doesn't matter from a technical point which time servers you use but normally you'd use ones near to you geographically. This has nothing to do with time zones but just efficient use of the Internet. Why reach across the world for a time check when a server in your own city is just as good?
It's because many time servers have access rules, they are only available to people in a particular area or other organizational affiliations.
Once you have entered your list of servers you need to enter the following at the command prompt:
W32tm /config /update
This tells the time sync service that there's configuration changes and to use the changed settings.
If you are a network administrator you might want to consider the effect of each computer connecting to the Internet for time checks. While it is not a big load you might want to nominate a computer / server in the office as the time source. That computer can do time checks to the Internet while all the other computers in the office check off it using the NET TIME command.