The Collaborative International Dictionary
Dominion Day \Do*min"ion Day\ In Canada, a legal holiday, July lst, being the anniversary of the proclamation of the formation of the Dominion in 1867.
Wikipedia
Dominion Day is a commemoration day of the granting of national status in New Zealand, and was the same in Newfoundland until 1949 and Canada until 1982.
Usage examples of "dominion day".
I have heard it recited often (sometimes even in Indian costume) at church socials, political picnics, Dominion Day Celebrations, and kindred uproars, and it never fails to rouse the audience to blood-thirsty fury -- sometimes directed toward the foes of their country, and sometimes toward the elocutionist herself (for it is generally assumed to be a piece for a lady to speak).
Mother used to talk to me, when I was a child, on Dominion Day as a usual thing, about loving Canada.