I checked with Campus Security, and this is what they told me:
Monday-Thursday: 8 a.m. to midnight
Friday: 8 a.m. to 7 p.m.
Saturday: 10 a.m. to 6 p.m.
Sunday: noon to midnight
Just tried to get into the lab at about 11:30ish, and the building was open but the lab doors were locked. Wouldn’t recommend that my fellow procrastinators test that midnight closing time as it seems they may close early some nights.