Do I have to move into college on my igned 'move-in day'?

I'm about to start my first year of college at East Carolina University, and I'm staying in a dorm. I received a brochure telling me that I was supposed to move in August 18th. However, I have a family vacation planned, in which I won't get back until the 19th. Can someone tell me if it'll be a big deal to move in two days later, since cles don't start til' the 20th? I'm going to call the place to find out Monday (as they're closed weekends), but I'd like to know now, so I can cancel the vacation plans. Anyone have some experience with this situation?