When you enter Canada you will either be given a specific date in your passport or it will have nothing entered by CBSA. If the latter you can stay only for 6 months only from entry date.
A visa validity date only determines the time period for when you are authorised to travel to Canada . Whether you are allowed to enter Canada and for how long is determined on arrival.
If you want to stay longer then your authorised stay look up the extend stay as a visitor process.