computer losing/gaining time

I'm running Windows 7 on an HP Compaq d530CMT; it's a Pentium 4 with 4GB of RAM. Obviously, it's an older machine; I don't know exactly how old it is but I believe it is at least 8 years old.

Recently, the time has been getting off. If it were losing time, I'd suspect the CMOS battery on the motherboard needs replaced. But, it's just been erratic; it gains and loses time. Earlier today, it was about 20 minutes ahead. I've done nothing to correct it and now it's only about 5 minutes ahead.

I always thought a weak CMOS battery normally causes a computer to lose time, not gain, and not jump around in such as way that it's ahead, then later ahead less, and then maybe behind, then ahead again, etc.

Still, I guess replacement of the CMOS battery is the logical step to start troubleshooting this. Any other ideas?

 

You appear to have hit the nail on the head.

Dying batteries can give unpredictable levels of power, leading to the computer failing to compensate properly for the change in supplied voltage, leading to erratic time.

Replacing the battery should fix the problem for a minimum of cost.

 

Thanks to both of you. nac4ev, that is my motherboard. I have replaced the battery and that has stopped the problem.