Your CMOS battery that maintains the BIOS (and clock) information could have run out. Change it, it is usually a CR2032 battery and really easy to swap out on your motherboard.
CMOS battery, bug in the OS, I have seen it under systems with a heavy load losing time. Possible when you run down the battery and it goes to sleep or hibernation you lose time. If it's a new laptop I wouldn't worry about the CMOS battery, just use NTP.
