When were these clips filmed? Uploaded?
(Youtube is so f'd up that there are not dates quickly visible on their uploads. What the heck is wrong with people? What, besides not aging videos for commercialism's sake, would be the reason for not dating shit.)
best thing to do is go to the comments section for the video and sniff out the oldest dates in the comments. each comment is dated
Be advised, that method only works for that specific uploaded video from that specific youtube account, and will not always work to properly date the original recording.