I have an ASUS K501U running Windows 10. From the get-go, it had issues with the clock. It would change the date on its own, regardless of using automatic time setting or not, or the time zone. As far as I recall, it wouldn't happen during use, but only after sleeping / hibernating / restarting / turning off. And it wouldn't change the time, only the date, typically a few days ahead.
I found several sources that mentioned that it was the BIOS battery which had to be replaced, but no conclusive information on the issue.
What is the solution?
PS: I have found also references to this same issue with other ASUS laptop models, a few years ago.
A few related links