The Day after Thanksgiving. It is always a friday, because Thanksgiving is always on Thursday. Most, if not all, retail stores, malls, etc. have big sales on Friday because almost everyone has the day off and are with family and can go Christmas shopping.

(Does Canada do Thanksgiving?) I thought it was an American Holiday but I can see how this could be a spill-over event seeing when the land was "found" by whitey there wasn't a division between the US and Canada, or an US and Canada for that matter.