Canada Day, Canadian national holiday, celebrated on July 1. It marks the anniversary of the unification of Upper and Lower Canada (what are now Ontario and Quebec), New Brunswick, and Nova Scotia as the Dominion of Canada. This union was effected by passage on July 1, 1867, of the British North America Act. Formerly known as Dominion Day, the name was changed to Canada Day in 1982 when the constitution was revised. The day is marked throughout Canada by parades, fireworks, and the display of flags.