Sith51 said:
Are you absolutely sure? Say I got my introduction letter in May and my program begins in September, would they still let me in?
Hi,
1. Not so early. In such a case, not only at port of entry (Canada), but one may also face "big problem" at port of exit (of your homeland).
Here, I quote one such unique case;
"actually my problem is that i got my visa in end of august and buy a ticket of 20th September's ticket but on port Indian immigration personal prevent me to go ahead because they ask for extension letter because they i am late for September classes which were already started on 1st September, i told them that on my offer letter there are two more intakes offered to me of January 2012 and May 2012 i will join January2012 intake, but they said that we can't allow you to go ahead too early for January 2012 intake, after that i talked with university they issued me a letter for January classes now i plan to go in first week of December, will they make a issue that you have your visa in augustbut why you are coming too late?"
Source: www.canadavisa.com/canada-immigration-discussion-board/anybody-share-hisher-port-of-entry-experience-or-any-one-what-could-they-ask-t85688.0.html;msg1056793#msg1056793
So to be on a safe side, follow the USA law of ONLY 30 days in advance.