So this dosen´t have a yes or no choise right? I just challenge somebody out of the bloom? I think thats a thing worth looking into. That you first make a challenge and the other one has to accept it. That will probably get rid of those who will post as small date as possible and use theyre uploaded video several times.
That's actually how it works already. The battle doesn't start until the other person accepts the challenge (they can also choose to decline it).
That is why you specify a "length" instead of a "deadline" when you create your battle. The deadline is set as "current date/time + battle length" once the other person accepts the battle. The challenger can also choose to cancel their challenge.