VM unregisters because time change automatically. It is faster than ddc time, and modify it, it will be back to the wrong date and time.

Solution 1

Windows: Set a new DWORD RealTimeIsUniversal to 1 in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TimeZoneInformation

Solution 2

Install all the Windows patches.

Problem Cause

Common cause of exactly these symptoms in dual boot Windows/Linux systems: the two OS' treat the CMOS clock differently and fight over setting the clock the way they want (Linux to UTC doing daylight savings etc. in software, Windows to local time so the software and hardware clocks are the same). This has a simple solution: tell one of them to use the other's default behavior.