My block on the 29th went from approximately 8am (check-in) to 11:30am (when I was asked to check out because I had an interview before 11:15am.
They do an hour-ish long presentation on the school and stuff where the dean and the associate dean talk. Then they pass out little cards to tell you when your interview is. When you're not interviewing, you can be taking a tour or writing your essay.
So, depending on your interview time, you could be there until maybe 4:30pm or so.