[za_claws]

It would take some wizard to alter this in a series of image files without introducing some inconsistency. Much less be able to upload the altered image back to the camera/phone.

particularly on a phone with the time being set by a NTP (Network Time Protocol) Server, getting time from an atomic clock.

[js1138]

This is CIA level stuff. If you alter the metadata in an image file, you introduce all kinds on inconsistencies. Not the least of which is that every image has to be consistent with all the others. I'm sure it can be done, but I hardly think a bunch of kids could learn to do this in a couple of days and get away with it.