I don’t know about online data, but with general applications, i.e., Word, Excel, etc., you used to be able to set the computer’s calendar and/or clock to an earlier time, create/modify the document, save it, and that’s what would show up in Summary or Properties. That was years ago; not sure if it’s still possible.
The programs that initially create and tag the files with the created/modified data use the system clock. It would be easy enough to reset the system clock to a previous/later date and copy the data from the original document to a document created with a modified system clock. Possibly tedious. I haven’t had reason to search out if there are any apps that would allow one to modify that data w/o going through a process like that though. If you just copy a document on the hard drive, it show the original data. I haven’t played to see if copying it to an external drive might provide new data and also remove/modify the version history.
it can be changed to show any modification timestamp even with a simple “touch” command. That being said, there are ways to reveal the modifications (that would also show some intent depending on which side of this you argue). Forensics evaluation could reveal the modifications. Another (and even simpler way) is if you can get copies of backup media and especially detailed logs from the backup software. The logs will show the previous timestamps of the files that would show something different than what they provide. The backup media will also show a timestamp of the file before it was changed. The timestamp of the file on backup media cannot be very easily modified (depending on the backup method and software used).
Timestamps on a computer can be modified using the command line “touch” command.
Answer is yes. BUT if it got on the net very hard to wipe it all. If it was on a local network then a competent IT guy could do it. Like others said several locations for dates, time etc. If there are images involved you need an expert to trace them.