My computer clock keeps moving ahead one day despite battery change and correcting date in BIOS. My system is Windows 7

Do you mean it moves ahead just once after you reset the day, not add a day every day?
Control Panel, Day and Time, Change Time Zone should do it.

Please don't negative responders for giving you information just because it's something you tried or it isn't helpful. Negatives are for factually incorrect answers. Maybe someone else is willing to tell you the next thing to try...

JoyPulv, didn't mean to negative you. Thanks for your help. Any other suggestions are greatly appreciated.
SMPalmer