Until someone invents a time machine neither is provable and maybe not even then. Put it this way any God capable of creating this universe woud have had to exist prior to and further would therfore exist exterior to it. Similarly such a God could have created it at any point in it's history he wished and we who dwell wholly within the universe would have no real way fo knowing anything other than the apparent age of this universe which could be drastically different from the actual age of this universe.