Have you applied or been accepted yet? Fall Advantage dates are May and June but regular Fall arrival dates don't begin until August. You get to pick between whatever dates are available in your season (for example, if you're accepted for Fall Advantage, you can't pick a regular Fall date), but since it's late in the cycle I think they've started closing some of them already. And I'm not sure what the exact dates are, sorry!
If you haven't applied yet, just pick regular fall and you should be fine.