It should be 5 p.m. Or 4:50 at the latest. Most WDW park restaurants take ADRs up until closing time.
We were there in Sept. during EMH (closed at 8 p.m.) and we had a 7:50 p.m. ADR.
The place was empty which was a surprise since I had a hard time getting an ADR. I mean there were only a few parites there.
Great thing was when we left the park was empty. We took our time having the park to ourselves. Made it worth eating there as we weren't too impressed with the food.
We had ADR in Sept '08, the park closed at 5:00 and I got 5:00 ADR. I will not do that again. Once the food ran out they didn't replace it so our choices in food as very limited. The CM there was very nice and friendly.