There's 2 solutions I could come up with.
To test if it is an OS problem, just log into the BIOS (since it has a clock too) and leave it there. Wait for as much time as needed and see if something happened.
If not, your OS is the problem. To solve it as an OS issue, you better try to erase recent updates, don't know if my guess is right, but a bad update may have screwed your clock.
Is it does, try cleaning the BIOS. If you want to try, go for a BIOS update, too. Maybe it does something, right?
Again, I came up with those. If they work, I don't know.