I interviewed in October. The interview is thursday so you need to arrive wednesday. If you aren't interviewing at Caltech you can leave anytime on friday but I wouldn't recommend leaving early like I did. The day is really long (8am to 10pm) because there is a dinner and afterwards the students take you out (which is optional). I wish I would have stay longer on Friday plus I was exhausted! Anyway, it was a really fun trip and I LOVED UCLA.