Canada as a nation was born in 1867. Today is our 146th birthday. Celebrations all over the city and country. Most stores and offices closed. Libraries, city offices, government buildings, post offices & banks closed. Canada Day celebrates the signing of the British North America Act (today called the Constitution Act, 1867), which united three British colonies into a single country. Originally called Dominion Day, the name was changed in 1982, the year that Canada gained full independence from the United Kingdom.