When you review a quiz attempt, then under each question, you should see a history of their responses. That will show you fairly accurately when each file was uploaded, I think.
Quiz
Quiz
གྲོས་བསྟུན་འདི་བསྡམས་ཡོདཔ་ལས་ ལན་གསལ་བརྐྱབ་མི་ཚུགས་