Normally the default time / date a camera will use if the RTC battery have failed to save the time/date is a older one in the past, so if you have that problem, but your memory card is full, then your first file saved will use that old default time / date, but then as the GPS is fixed and the time now correct, when the next correct timed file is going to get saved, and the memory card is full, your first recording with the old default time / date will be deleted to make room as it is the oldest file on the full memory card.
So if you later review your memory card you will not have a strange old time/date file on there, but you might notice your last drive start so to say X minutes down the road depending on the segment size you use.
On the other hand if you do not use GPS and have a reset to default problem, which then probably happen on every start of your car, then you have problems as you will be "groundhog" driving and doing so with the same default time/date for each drive, and those will always be the oldest ones on the memory card, so its just a big old mess to put it lightly not least if you have a event.
I just named the problem groundhog driving after the movie "groundhog day" where the guy relive the same day over and over, just like your dashcam would if it woke up every drive with the same time / date to go by.