How did Canadian Thanksgiving start?

Martin Frobisher and his men celebrated in 1578 surviving a harsh winter near Baffin Bay in Canada. The French settlers under Champlain also had a fall harvest. The Loyalists who fled to Canada after the American Revolution brought the Thanksgiving custom with them along with the idea of turkey, and pumpkin pie. It became a national holiday in 1879 but in 1957, the date was changed to the second Monday in October.