The 12th Canadian Parliament was in session from 15 November 1911 until October 6, 1917. The membership was set by the 1911 federal election on September 21, 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.