The time/date stamps on the photos really aren't "hard evidence". After all, one of the guys at the party had control over the settings ~
I believe they were using their cell phones and they are connected to GPS and "Perfect Time". The system you are speaking of is archaic.
First, the provenance of the time-date stamps are born out by other facts and observations. Second, the date/time stamp can only be adjusted prior to a photo being taken, not after, in terms of photos already taken. Third, the camera has been examined by technical experts who state that it had not been adjusted.