The prom started at 7pm in my game but when the teens were hanging out at a friends house, everybody left early around 5pm. I didn't know what was going on and nobody was dressed for prom at the friends house. I'm not sure if they were suppose to be. I went to the auditorium and things weren't set up yet until 7pm came and the prom build started happening right before my very eyes. I was able to change my active sim character into her formal wear but her NPC prom date was in his everyday clothes still. Everybody else who came changed into their formal wear clothing. I've only played prom once yesterday, so I'm figuring out things too.