Time/Date in Win98

I have weird thing happens to some of my PCs continuously running. Once in a while the date on them jump a few days ahead (time stays more -less correct). After I reboot PC and check CMOS, the date in CMOS is correct and when Windows comes up – thedate is correct too. Looks like Windows picks up the date/time during boot, but why does it jump ahead while running. Another possibility is that users change the date, but considering line of work we do – there is no benefit from it. Does anybody know about such behavior in Windows, and how to control it?

Thanks

GRiG