Have you tried changing the CMOS battery?
My HP DV6113US running XP loses time on the start bar clock if it does not have either AC or a battery attached to the unit. When I say losing time I mean hours over just a day. If you leave the battery pack or AC attached, it keeps perfect time. Shouldn't the internal CMOS battery keep the correct time even if there is no other power source attached? I have at times put the laptop in the bag without a battery attached and left it for several days, usually in hibernate. Should this have caused the CMOS battery to deplete? The unit is less than a year old and still has a month of warranty. Would you suggest I send it in to HP, or is there something here that might be an easy fix without having to give up the computer for two or three weeks?