e) Applicant Response Periods. Allow an applicant who has been given a provisional or final acceptance between December 1 and December 31 of the academic year prior to the academic year of matriculation a response period of no fewer than forty-five days to reply to the offer. For applicants who have been accepted between January 1 and January 31, the minimum response period shall be thirty days, and for applicants accepted on or after February 1, the minimum response period may be reduced to fifteen days. The response period may be lifted after July 15, or two weeks before the beginning of the academic year, whichever comes first.
This is from ADEA guidelines.