That distinction matters because the Canadian formula rewards a longer ownership history proportionally rather than requiring a fixed minimum period to qualify at all. A property owned for two years and used as your principal residence the whole time can still qualify fully.
Where timing does matter is a change in use. Converting the home to a rental, or back again, and a period during which it was not your principal residence, both affect the fraction of the total gain that the exemption ultimately covers.
This is general information, not tax advice, so confirm your specific designation history with a tax professional before you list, since this is a federal income tax formula and has no connection to the City of Saskatoon's 80 percent property tax assessment. Get your hand-reviewed valuation from Joel Dyck.