The day that each school begins the first day of classes is usually the last day that you can be sure you're not getting in.
However, I have designated May 10th my panic day, even though it is very likely I will get in in July.
On May 10th I will start studying fot the August MCATS, and I will study hard until I get in. (That's the day of my last final exam)
If you're not in yet, I would also recommend starting a new EC. You don't want to hand in the same amcas application again! 🙂