Hi cazace2,
There are probably a dozen system and software ways that this problem could arise, but I think the most frequent problem relates to a weak/failing CMOS battery.
Since it's cheap and easy, you might consider popping in a fresh battery.
If the problem persists, we can investigate further.
(about $2.50 for the battery at RadioShack, Best Buy, Office Depot, or most electronics stores)
Best Regards