Section 4 of the Canadian Charter of Rights and Freedoms

Section 4 of the Canadian Charter of Rights and Freedoms is one of three democratic rights sections in the Charter. Section 4 guarantees that federal and provincial elections must take place from time to time. Subsection 4(1) provides that the maximum term of the House of Commons, and of all the provincial legislative assemblies, is five years. Under subsection 4(2), an exception is made if war or rebellion causes two-thirds of the membership to believe a House of Commons or legislature should last longer.

The section reads,

(2) In time of real or apprehended war, invasion or insurrection, a House of Commons may be continued by Parliament and a legislative assembly may be continued by the legislature beyond five years if such continuation is not opposed by the votes of more than one-third of the members of the House of Commons or the legislative assembly, as the case may be.

Section 4, with the Charter and Constitution Act, 1982, came into effect in 1982. However, similar provisions had existed in the Constitution of Canada prior to that time. For example, the fact that a House of Commons could not last more than five years was first set by section 50 of the Constitution Act, 1867. It reads,

Although section 50 names the Governor General of Canada as the official who may call an election early (and section 4 does not specify an official), usually the Governor General acts on the advice of the Prime Minister of Canada. Before and after section 4, the Prime Minister may call an election early simply because he or she feels it is the right time, or because he or she may be faced with a non-confidence motion.

In 1916, an exception was made to the rule so that a House of Commons could last longer than five years, but this had to be done through a constitutional amendment, namely the British North America Act, 1916. The rule was also going to be entrenched in the bill of rights in the proposed constitution of 1971, the Victoria Charter. However, this was never enacted.

...
Wikipedia