Context : The Letters Patent, 1947 (more formally, the Letters Patent Constituting the Office of Governor General and Commander-in-Chief of Canada) are a legal instrument introduced by King George VI, which came into effect on 1 October 1947 and continue to, along with parts of the Constitution Act, 1867, constitute the Office of the Governor General. 
Answer : 1 October 1947
The point in time of Letters Patent, 1947 was when?