I think October 15th is the magical date for Early Decision programs. If you applied ED to one school, and they choose not to accept you in the ED program, they have to release your application to any other schools you wish to apply to. So, yes, if you were accepted Early Decision by a school, you already know. But for the normal admissions program, I don't think there is any magical deadline. October 15th is awfully early, but I imagine some people may have already heard. I do think that by some date (I believe its May 15th) you are no longer allowed to be holding on to 2 or more acceptances from different schools, and must choose one.