May 24 has since 1901 been celebrated throughout the British Empire as Empire Day. An amendment to the Statutes of Canada in 1952 moved the holiday to the the Monday preceding May 25. From 1953 Empire Day was made the date of the Queen's official birthday in Canada by annual Vice-regal proclamation, the link being made permanent in 1957. In 1958 Empire Day was renamed Commonwealth Day.
This is the first of the summer long weekends in Canada. Known colloquially as "May two-four weekend" (a two-four is a case of 24 bottles of beer).
In Quebec, the Parti Québécois government renamed the holiday Dollard des Ormeaux Day, and in 2002 changed that to la Fête des Patriotes in honour of the Patriotes Rebellion. Most Anglophone Quebeckers continue to call it Victoria Day.
See also Commonwealth Day