Nope, not September! Actually this year you can start using it August 19th:
McMASTER UNDERGRADUATE, GRADUATE AND MOHAWK COLLEGE STUDENTS
If you are a full time undergraduate or graduate student at McMaster University, or a full time student at Mohawk College, your bus pass is included in your student fees. The pass will entitle the holder to unlimited travel and is valid from September until April for McMaster Undergraduates / Mohawk College students and from September until August for McMaster Graduate students. You will obtain your validation sticker at time of registration and it must be placed on your Student Identification Card. When boarding, show the driver your Student Identification Card with the sticker attached to get to your destination. Fall/Winter 2013/2014 stickers do not entitle students to ride HSR until August 19, 2013.
Source:
http://www.hamilton.ca/CityServices/...nd+Conditions/