CMOS Settings Wrong/CMOS Date/Time Not Set

This appeared on my computer just this morning.When I went to windows the date and time was January 1,2002 and 12:00am.Then this evening it appeared again CMOS Wrong I tried pressing F2 to reset to default still nothing happened it is still January 1,2002 and 12:00am.

What do I do?I don't know how to set this CMOS.

Thanks.