bad system date

What can cause bad system dates? I'm at school and on one of the computers whenever I log on I can basically have any program for free as long as they release a trial because it never keeps track of the real system date (i.e the program expires january 0, 0000). It's in a networked environment but I only have this problem on one computer. What could be causing this? Oh it's on NT (xp).

did u try running the sync? I dont know if it would affect xp's time but as bad CMOS battery can mess up the out-of-windows time...