Urban Dictionary:
Queen Victoria's birth day, May 24th, is a statutory holiday in Canada and the first long weekend since Easter. It is the traditional weekend during which one opens 'the camp' (cottage), and signifies the start of summer (and Blackfly season) in Canada. The reference to 'two-four' rather than 'twenty-fourth' is a Canadian inside joke refering to the obligatory case(s) of 24 bottles of beer, or 'two-fours' required to celebrate the opening of the camp and to steel one's courage against the blackflies and the mice that will have settled into the camp since it was closed in the fall.