Must I leave Canada by the valid until date on my temporary resident visa?
No. The date on the temporary resident visa is the date by which you must arrive in Canada. The border services officer at the port of entry will decide how long you can stay in Canada. The officer will use one of three ways to note how long you can stay.
The officer may stamp your passport and write a date under that stamp. If so, you must leave Canada by that date.
The officer may stamp your passport without writing a date under that stamp. Instead, the officer may give you a visitor record. If so, you must leave Canada by the date shown under “Valid until” on that visitor record.
The officer may simply stamp your passport without writing a date under that stamp or giving you a visitor record. If so, you can stay in Canada for six months.