Philadelphia is 13 hours behind Shenzhen
There is no standard 8-to-6 overlap. Someone joins early or late.
Shenzhen and Philadelphia are too far apart in time (13 hours) for their workdays to line up during regular hours. For anything urgent, agree on an early-morning or late-night bridge hour in advance so nobody's caught off guard. The window above shifts seasonally: Philadelphia keeps daylight saving while Shenzhen ignores it.