Copenhagen is 6 hours behind Shanghai
Best overlap: 2:00 PM to 6:00 PM in Shanghai is 8:00 AM to 12:00 PM in Copenhagen.
Plan around 2:00 PM to 6:00 PM in Shanghai, which is 8:00 AM to 12:00 PM in Copenhagen, to catch everyone during office hours. Since Copenhagen is 6 hours behind Shanghai, the workdays overlap by around 4 hours; 2:00 PM in Shanghai (8:00 AM in Copenhagen) makes a reliable recurring slot. For part of the year the maths changes: Copenhagen observes daylight saving, Shanghai does not, shifting the overlap by an hour.