As I understand the parliamentary system, there are circumstances under which new unscheduled elections are held. If a governing coalition falls, there's a vote of no-confidence, or if certain people just ask for it, there's an election, any time of year. How long does it typically take for such an election to happen after they're called for? And how, from a practical standpoint, are snap elections managed?
In Canada, when a government falls through a direct non-confidence motion , or after having been defeated on a bill deemed a confidence motion , the Prime Minister, almost immediately, will go to the Governor General and advise him/her to call an election on a certain date. For Canadian Federal elections, there is a minimum campaign period of 36 days. The longest election period in history was 74 days.
Typically, after the writ of election is returned (i.e - the election has been held, and all votes counted) there is a 30-60 day transition period where the former Prime Minister continues to sit, and the incoming Prime Minister gets his/her cabinet together. The parliament does not sit until the new government is in place, and the old government cannot pass any legislation. That is, it is a caretaker executive.
So, assuming minimum times, it takes on the order of 2 months to toss out and replace a Government.
The Governor General does not have to follow an election request, and can decide to try and form a government from the existing parliament that can gain the confidence of the house. This is rare, and would require a coalition between the Second and Third parties. In this situation, a government can be replaced almost immediately, but it just doesn't happen.