are you talking about the summer program? coz wouldn't you have to choose your dates since it depends on when your uni goes on summer holidays and when you return to the next semester?
I am talking about the summer program, yes. You would need to choose from the list of dates Disney provides depending on your university term time, yes, but you are limited to the small number of dates which they offer you. As I said, last year participants had the choice of four different start dates, but the end date was the same from everyone.
