Calgary is 11 hours behind Karachi
There is no standard 8-to-6 overlap. Someone joins early or late.
Practically speaking, Karachi and Calgary never share office hours; 11 hours of separation keeps their days apart. To talk live, someone has to flex: an early start in Calgary can catch the tail end of the day in Karachi, or the other way round. The difference isn't constant year-round: Calgary adjusts for daylight saving while Karachi holds steady.