I have a single server that is also a domain controller in a cabinet, there are no other servers attached to its domain. I've reset the time in the BIOS (from what I recall) and in Windows to the current correct time, over a period of a few days the time will be off by about 20 minutes.
Since it's a DC it shouldn't be getting time over NTP, correct?
Does this mean the issue could be with the BIOS battery? The server is almost 4 years old and the CMOS battery is original.