Under legislation passed by Parliament, federal elections must be held on the third Monday in October every four years following the most recent general election. The Prime Minister may ask the Governor General to call an earlier election.(emphasis mine)The original intent of the electoral law was to take the power of calling snap elections out of the hands of the PM. Stephen Harper said so himself in 2006:
"Fixed dates stop leaders from trying to manipulate the calendar. They level the playing field for all parties,"....Last fall, Harper used "parliamentary disfunction" as his excuse to break the spirit of his fixed-election date law. Now, the government is telling new citizens that even that pretense is unnecessary. Stephen Harper, it seems, can call an election any time he wants one. We have come full circle.
"Hopefully, in the next election, we can run on our record and we won't need the manipulation of the electoral calendar."(Toronto Star, September 4 2008 A16)
Update: I like Robert's take on the document as a whole. Recommend this Post