The Canadian Citizenship Act 1946 comes into effect, converting British subjects into Canadian citizens. Prime Minister William Lyon Mackenzie King becomes the first Canadian citizen.

The Canadian Citizenship Act was a statute passed by the Parliament of Canada in 1946 which created the legal status of Canadian citizenship. The Act defined who were Canadian citizens, separate and independent from the status of the British subject and repealed earlier Canadian legislation relating to Canadian nationals and citizens as sub-classes of British subject status.

The term "British subject" has several different meanings depending on the time period. Before 1949, it referred to almost all subjects of the British Empire. Between 1949 and 1983, the term was synonymous with Commonwealth citizen. Currently, it refers to people possessing a class of British nationality largely granted under limited circumstances to those connected with Ireland or British India born before 1949. Individuals with this nationality are British nationals and Commonwealth citizens, but not British citizens.

Canadian nationality law details the conditions by which a person is a national of Canada. The primary law governing these regulations is the Citizenship Act, which came into force on 15 February 1977 and is applicable to all provinces and territories of Canada.

January 1 is the first day of the calendar year in the Gregorian Calendar; 364 days remain until the end of the year. This day is also known as New Year's Day since the day marks the beginning of the year.

William Lyon Mackenzie King served as the tenth prime minister of Canada for three non-consecutive terms from 1921 to 1926, 1926 to 1930, and 1935 to 1948. A Liberal, he was the dominant politician in Canada from the early 1920s to the late 1940s. With a total of 21 years and 154 days in office, he remains the longest-serving prime minister in Canadian history.