system time mysteriously changes

[Kevin Smith]

I'm having a problem with my system clock.  The time will be fine for a 
few days, then all of a sudden, I will notice that it has jumped ahead 
by a number of hours (usually enough to change the day to the next day). 
I can confirm that the time has changed on the system cloth in the BIOs 
setup as well.  This has happened once every few days.

I thought it may be a clock battery problem on the the motherboard, but 
I am thinking that this is not the case as the minutes are usually OK - 
it is just the hours/day that changes.

Another idea that I had was that because I am dual booting windows (on 
occasion) and freeBSD, windows may be the culprit, but  I verified that 
by rebooting windows, it is not resetting the system clock.

Any ideas on what could be wrong ?  I also have ntpd running, which I 
used as an attempt to keep the clock set correctly (in effort to find a 
solution to the problem), but it does not appear to be able to handle 
correcting the time.

How can I debug who/when is changing the time on the clock ?

thanks,
-Kevin