The 12th Canadian Parliament was in session from 15 November 1911 until 6 October 1917. The membership was set by the 1911 federal election on 21 September 1911, and it changed only somewhat due to resignations and by-elections until it was dissolved prior to the 1917 election. At 5 years, 10 months and 22 days, it was the longest parliament in Canadian history. The parliament was extended beyond the normal limit of five years by the British North America Act, 1916 as a result of World War I.