Game time and Clock time are out of sync.

For some reason the game time appears to be behind the clock time. The clock time will show something like 7pm but if go in to CAS and back out or to World edit and back in then it'll reset to an earlier time before eventually going out of sync again. This means all time based activities such as work or school occur several hours after the clock says they should or time specific events can't be kept track of.

I've tried repairing in origin, clearing the cache, resetting, removing all CC and mods before testing then adding back one by one and nothing seems to make a difference except a brand new save with a whole new sim which is really inconvenient and still carries the worry that the issue will eventually reoccur as I don't know the cause. Does anyone know what might be the cause or solution to the issue please?