Campgrounds open for initial entry at 12 p.m. on Wednesday if you have a Wednesday Camping Party Pass. Otherwise, it opens for initial entry at 9 a.m. on Thursday. After that, you can enter and exit at any time.
The box office for initial ticket scanning is open Wednesday from noon to 11 p.m. and open Thurs, Fri and Sat from 9 a.m. to 11 p.m. If you show up for the first time - for your initial ticket scanning - after 11 p.m., you will have to wait until the next morning to enter the campgrounds. You can stay out front in the staging area that night, but be aware that there is NO security out there over night.