On what date did three British colonies unionized to form the federal dominion of Canada ?
Specifically , the preamble of the act states : " Whereas the Provinces of Canada , Nova Scotia , and New Brunswick have expressed their Desire to be federally united into One Dominion under the Crown of the United Kingdom of Great Britain and Ireland , with a Constitution similar in Principle to that of the United Kingdom ... " Furthermore , Sections 3 and 4 indicate that the provinces " shall form and be One Dominion under the Name of Canada ; and on and after that Day those Three Provinces shall form and be One Dominion under that Name accordingly " .