Not your problem. You didn't change your plans, they moved the deadline. When that was discussed you should have been sure to mention that is after your planned

Not your problem. You didn't change your plans, they moved the deadline. When that was discussed you should have been sure to mention that is after your planned/announced departure, if you didn't voice this before be sure to re-iterate it now. Make your focus on supporting your team in knowledge transfer and making sure they are confidant they can continue without you, not so much helping them hit that date. If they ship a few more weeks late but are successful that's much better than if it blows up and they end up scapegoating you, but either way you're already out the door. You can submit a letter of resignation now with your planned end date. That helps remind that it's not a negotiation.