When Mitch, Frank, and Beanie decide that they are going to have a party they say the party is on a Friday night. When they show the outside of Mitch's house you see the sign for the party and it says the party is on Thursday at 9:00. Then when Frank talks to the guys with the beer bong he says that tomorrow he has a nice Saturday planned. If the sign is right then he would have a pretty nice Friday.
The man that shows up at the door to ask about the orgy, is the director of the movie: Todd Phillips.