https://en.wikipedia.org/wiki/Elections_in_Canada#Length_of_election_campaigns

In terms of days from writ to election day, the longest campaign was that of 1980 election, which lasted 66 days. The 2015 election, currently taking place, is 78 days long from writ to election day, making it the longest campaign for a one-day election, exceeding in length only by that of 1872.

Prior to the adoption of the minimum of 36 days in law, there were six elections that lasted shorter periods of time. The last of these was the 1904 election which occurred many decades before the minimum was imposed.

In practice, the Prime Minister will generally keep a campaign as brief as is legal and/or feasible, because spending by parties is strictly limited by the Elections Act. The maximum spending by each party is increased by 1/37th of the maximum for each day that the campaign exceeds 37 days. The 1997, 2000 and 2004 elections were all of the minimum 36 days in length which has led to a common misconception that elections must be 36 days long. However, prior to 1997, elections averaged much longer: aside from the 47 day campaign for the 1993 election, the shortest election period after World War II was 57 days and many were over 60 days in length.