Hi there, this is probably impossible but thought I would ask. Would anybody know how to backdate a previously published Youtube Video? eg. If I posted a youtube video today, in a few days I could edit it to say it was published in May? Thanks in advance

I would imagine it would be impossible. That is the kind of data that by definition needs to be generated automatically, and cannot be manipulated. Otherwise it would be completely meaningless.

You can not modify the date but you can use YouTube for a box prediction kind of routine. Force some things( word , number , design) and then make one of the selection a free choice between a reduced number of items. Record a video of each out together with the forced items and post them separately in your YouTube account as private. During the show make public the video with the freely selected choice.
The video will have the date you posted it in YouTube as private.
Regards

Check out Tube by Jason Messina, or perhaps Tube 2. Not sure if it's still a viable method as I've not used it but may be what you're looking for.

YouTube doesn't allow you to customize a link, or overwrite an existing link to a backdated video. I have used Photobucket; back in the day, to have a prediction match on a future date.

What you can do, is make several prerecorded predictions on YouTube and use obfuscation (redirect) to the correct link. Such as, youtube.com/watch?v=mMLnxf8DE5I