Many schools let you pick a date. I didn't have Friday classes this semester and I was able to schedule 4/7 interviews on Fridays. Of the other 3, 1 was on a Monday, 1 on a Wednesday, and 1 on a Thursday. My advice would be to try to have one day of the week off so you can schedule interviews for that day if you can. Mondays and Fridays are good days because you can have the weekend for travel time. Ultimately though, you will probably have to miss a day of class at some point.