Montreal is 13 hours behind Shenzhen
There is no standard 8-to-6 overlap. Someone joins early or late.
Shenzhen and Montreal are 13 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 Shenzhen and Montreal so the burden doesn't fall on one team. Because Montreal and Shenzhen don't both observe daylight saving, plan to re-check the overlap around March and November.