Quite simply, if a monster card's effect can be used during your opponent's turn it will say so on the card or will have an activation timing written on the card that can be done on your opponent's turn.
If the card does not specifically say it can be used during your opponent's turn, it most likely cannot. All ignition effects (DAD's effect is an ignition effect) can only be activated during MP1 and MP2 of YOUR turn.