You must ensure that you leave Canada before your allowed stay period expires.
If you are allowed a six-month stay then you must depart the country before the six month period is over to avoid the rejection of a future eTA application.
If you want to stay longer than your authorized stay, you should apply for an extension at least 30 days before the authorized end of your stay.
Apply for your eTA in 3 simple steps. Visit our website now: https://canada-eta.co.uk/apply-for-eta/.