Clock skew on FC13

[Alex]

Hi,

What could be the cause of significant clock skew? The PC operated
fine for quite some time, and either something changed or there is
something wrong with the motherboard, but the clock could skew an hour
in less than a 24 hour period. The PC is usually completely idle. It
has all regular x86_64 FC13 updates applied.

I've done a bit of searching online, but haven't had much success. How
can I go about troubleshooting this?

Thanks,
Alex