In this case, you are seeking a word that is not needed, because you are not worried about making it to some date, you are worried about making it to the show, now that it has been postponed. So, at least in this particular sentence, trying to use a word that denotes the date itself creates a need where no need exists in the first place.
On the other hand, if you truly want a word to refer to the new date itself, I'm not aware that such a word exists. "New date," "later time," or various versions thereof, work just fine.
As illustration, consider this: "Oh, it's been postponed. What's the new date?" Now try to think of any single word you might substitute for "new date." I can't come up with one (which doesn't mean there isn't one, but if there is one, I think it would be rather obscure).