Pretty much what rideltrain said. Officially, unless you're taking summer courses, you'll be on vacation from May 1st until August 31st at least (orientation for new students is the last week of August). Classes usually begin after Labour Day (1st Monday of September), but this is not guaranteed. The Christmas break is from December 24th to January 2nd inclusive, but depending your exam schedule (and whether or those dates are during or around weekends), your vacation might begin (much) earlier or end later. The only other breaks are Thankgiving (second Monday of October), Reading week (last week of February) and Easter (Good Friday + Easter Monday). There are no such things as snow days (exception: the Ice Storm of 98, lost 6 school days, 3 of which were regained by sacrificing Easter Monday holiday and pushing the end of classes right before exams). In the event of severe weather during exam period, time accomodations will be made (such as accepting students up to two hours late and giving 3 hours from each student's arrival).