Dominion Day was first established as a legal holiday in 1879.
Canada’s Confederation took place on 1 July 1867, when Nova Scotia, New Brunswick, and the Province of Canada joined to form the Dominion of Canada. The anniversary was celebrated informally from the beginning, but it did not become a statutory holiday immediately.
On 15 May 1879, the Canadian Parliament formally designated 1 July as Dominion Day. The name referred to Canada’s constitutional status as a dominion within the British Empire, a term drawn from the British North America Act, 1867.
A common mix-up is confusing 1879 with 1867. The earlier year marks Confederation itself; 1879 marks the legal creation of the holiday. Dominion Day was renamed Canada Day in 1982, during the same period that Canada patriated its Constitution.