ERAS file tweaking began July 1. You can begin applying to allopathic programs Sept 1 (both PM&R and prelims), and programs can start downloading your application file on Sept 1 as well. Some programs will wait until the Deans letter is released (Nov 1) before granting interviews, some will grant them sooner. You may have a wider selection of interview dates at a given program if you apply earlier, but because of the Match process, the rolling admissions mentality doesn't apply with regards to landing a residency. Although, for the independent applicant (IMG, DO, re-applicant, etc.) who potentially could be offered a pre-match, it may be beneficial to get your application done sooner rather than later. Not all programs offer pre-matches however, and deadlines will vary from program to program check w/ each one individually.