How to solve problem with time repeatedly being set incorrectly

For the past month or so, I had a couple of computers that kept on being set
to the incorrect time, and I couldn't figure out what the problem was. I
thought it was some weird application gone awry, but then I noticed getting
several e-mail messages from people where the time on their system was off by
the same amount.

I tracked the problem down to the "Date and Time" setting in the XP control
panel where the systems had been set to synchronise their time to the
time.windows.com server which apparently just has some bogus clock that isn't
calibrated to anything other than some guy's wild guess at what the time is.
Changing the server to the time.nist.gov server or disabling time
synchronisation fixes the problem. (Of course, you have to get the guy
sending you mail with the wrong time to fix his XP configuration as well).