Istanbul is 10 hours ahead of Vancouver

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

Vancouver and Istanbul are 10 hours apart, and that gap is wide enough that their normal 9-to-5 workdays never quite touch. If you meet regularly, fix one off-hours slot and rotate it between Vancouver and Istanbul so the burden doesn't fall on one team. Remember that Vancouver shifts for daylight saving and Istanbul doesn't, so recalculate the overlap after each clock change.