Montreal is 12 hours behind Shanghai

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

Shanghai and Montreal are 12 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 Shanghai and Montreal so the burden doesn't fall on one team. Remember that Montreal shifts for daylight saving and Shanghai doesn't, so recalculate the overlap after each clock change.