Calgary is 9.5 hours behind Tehran

There is no standard 8-to-6 overlap. Someone joins early or late.

Set against a 9.5-hour difference, Tehran and Calgary run their workdays on completely separate schedules. Block a single recurring off-hours slot that both teams agree on, rather than negotiating a new awkward time every week. Don't be caught out by clock changes — Calgary observes daylight saving and Tehran doesn't, so the offset varies by an hour through the year.