Last week it closed at 8:00pm. In October it closed at 10:00pm.
Let me just saw that the closing time last week seemed appropriate for the time of the year. It got pretty cold at night and while there were a few people in the pools, I wouldn't be paying lifeguards to sit there and watch basically no one.
That being said, the quiet pools stay "open" until midnight. While its not the same as the big pool, its still a nice break at the end of the day. My DD7 is happy to swim at the end of the night, even if its "just" the quiet pool.