No problem, it's some weird airline called Transat -- never heard of them. I just gave those two as examples, you should look on Kayak yourself. Buy two tickets, don't use Lahore as your starting point to Vancouver -- just go from Lahore to somewhere in Europe, Frankfurt, Schipol, or Heathrow. If you have to save money, do it by going one way, not by going late.
http://www.ca.kayak.com/flights#/FRA-YVR/2013-09-02
Also, it is not written -- I'm just telling you what I've experienced. Students who came to my class ten days late, failed. Why? Because they were ten days late. There's no rule.