I think date mention in you letter(WP-EXT only except PGWP) received after submission of application. It's generally, 120 days from the date of submission of application or decision made which come first. .
Ohh, do you applied PR under Quebec PNP ? As I know Quebec PNP is very frustrating. Took very long time. Therefore, I did not never think about this option. Although, I am in Quebec from last two years.