Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

The path to independence for the white colonies of the British Empire began with the 1839 Durham Report, which proposed unification and self-government for Upper and Lower Canada, as a solution to political unrest there. This began with the passing of the Act of Union in 1840, which created the Province of Canada. Responsible government was first granted to Nova Scotia in 1848, and was soon extended to the other British North American colonies. With the passage of the British North America Act, 1867 by the British Parliament, Upper and Lower Canada, New Brunswick and Nova Scotia were formed into the Dominion of Canada, a confederation enjoying full self-government with the exception of international relations. Australia and New Zealand achieved similar levels of self-government after 1900, with the Australian colonies federating in 1901. The term "dominion status" was officially introduced at the Colonial Conference of 1907.
When was it proposed to unify Upper and Lower Canada?