Same here. I was told when I made the reservation that I would need to check fireworks time in the times guide that week and again the day of and show up 1 hour before fireworks for the dessert party. I am not expecting the time listed on the ADR to change.
If it is causing a conflict with a dinner ADR that you want to make, you can call dining and they can override the system allowing you to have a dinner ADR and the dessert party. We did that so we can have a light dinner in the late afternoon before the dessert party.
I'm so excited to enjoy Christmas Eve fireworks without being trampled! See you there.