Yes it is 4pm but they will let you check in earlier if you want a bottom floor room. I got there at 2pm and they could put me on bottom floor. I waited got top floor and could watch fireworks with my kids on 8th floor
We got there at 1 PM on a Wednesday and they checked us in. We had a suite room on the 7th floor facing the park fireworks were great.
I believe 4PM but a phone call to them is the way to get a definite answer.
Thanks! Your answer is awaiting moderation.