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When did Guy Carleton, 1st Baron Dorchester's post war activities start?
Guy Carleton arrived in Quebec on 23 October 1786 to begin his governorship of Quebec after the American War of Independence.
What year is Guy Carleton, 1st Baron Dorchester's post war year?
1786 is when Guy Carleton began his postwar assignment to govern Quebec.

Question: what important thing happened in the period
Self-contained rewrite: What important thing happened in the period of Guy Carleton, 1st Baron Dorchester's governorship of Quebec?