No less than and no greater than
You often hear of the likes of Osama Bin Laden (actually, just Bin Laden I think) quoting certain events or holding a copy of a newspaper during video footage to prove unequivocally that the footage was taken after a certain event and therefore after the time of that event. But I often wonder whether anything could be used, likely something that we haven’t yet discovered, to accurately time-stamp a video. That is, confirm the exact timing of its filming, as opposed to giving a “no earlier than” date.
Because that would be kind of cool.