It is set GMT+10 so it is something else caused it
Does not really matter, I set it right when I posted and it is still right now a day later, think it must have Gremlins.
It has done it again, seems it has something to do with reboot, yesterday it did not change as I did not shut down, if it were cmos battery it should not be exactly one hour,any way only two days till the real thing.
the cmos battery only works when the pc is shut down, this battery holds the memory, so when you power up all is ok, however the battery does not last forever, please change it, only costs 3 or 4 dollars US.
also insure that your pc is free from infection, run a full scan with your antivirus and run a full scan with Malwarebytes free