Acceptance dates are on 4 specific dates. The first one is in October. No one will be accepted prior to that date unless you're in the guaranteed admissions program or early decision of course. So this is how it works, your application is reviewed by an evaluator and given a base score. Then you interview and your interviewer gives you a score. That base score, interviewer score is taken in front of a committee (20+ people including some 4th year medical students, Faculty PhDs and MDs). You interviewer will stand up and present you to the committee and they will finally vote you 1-5 and based on that if you score a 1 or 2 then you will be accepted as early as October. Your score DOES NOT change and you compete with other pools of interviewees that have scores. The highest scores get accepted the first acceptance batch that is in October, second highest on the second date which is in December and so on. Offers are sent on or about October 16, December 15, February 1, and then the class is completed on or about March 16. Sometimes offers can go out +1 dates from those specific dates due to some issues but most likely never earlier. It should be noted that once the committee gives you a final score NOTHING, absolutely nothing can change that not even the Dean of admissions can change that score. You can send in interest letters but they will be pointless unless of course you're the unlucky one that has to suffer through all 4 acceptance dates and still end up on the waitlist. I hope that clarified everything you asked.
(jk...)
