Karachi is 11 hours ahead of Calgary
There is no standard 8-to-6 overlap. Someone joins early or late.
Practically speaking, Calgary and Karachi 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. One seasonal catch: Calgary springs forward and falls back, but Karachi doesn't, so the gap changes by an hour for several months of the year.