I have had it happen a few times that the PC clock has been re-set for whatever reason (possibly with a BSOD issue but most likely caused by Malware infection) to the year 2099!
Usually it gets set to the 1/1/2099 with or without a different or wrong day of the Week, and while it isn't too much of a bother returning the date & time back in Windows 7 this is quite annoying to have to do but...
The bigger concern, especially if it is a form of hack vulnerability for a sleeping backdoor trojan or malware exploit that is activated when the system clock is adjusted to that ridiculously future arbitrary date a few things stop working properly especially security software with end date licenses, so they just automatically stop functioning.
Avast! is one such program that unfortunately stops functioning completely and fails like others to be allowed to update or re-start in 2099, IME. I've had this happen a few times in the past and figure that a full system reformat swipe and re-install ultimately is the most secure way to completely clean the PC in such cases where even after returning to current date & time scans can't find the fault or cause. (Which I had to do recently.)
While it may not be absolutely necessary to go through this extreme procedure, I find it loathsome that while the PC was unfathomably re-set to the year 2099 my Avast! resident AV had turned itself off no matter what the reason was for the PC year date change.
Because it is more than likely to have been a suspicious action and most likely to have allowed for further unchecked activities with Avast! and other security turned off, I think it would be good to have Avast! still fully function if the year is 'discovered' to be 2099.
Sure this won't prevent similar issues with inexplicable randomly year changes, but for some reason this year 2099 thing is pretty regular and might be a MS Windows default thing anyway, so it would help in these most frequent circumstances of this type of occurrence if Avast! could be somehow set to still fully function if the year 2099 is encountered.