Shenzhen is 7 hours ahead of Madrid
Best overlap: 8:00 AM to 11:00 AM in Madrid is 3:00 PM to 6:00 PM in Shenzhen.
Your window to reach both cities is 8:00 AM to 11:00 AM in Madrid, which converts to 3:00 PM to 6:00 PM in Shenzhen. Shenzhen is 7 hours ahead of Madrid, leaving about 3 hours of shared hours — plan recurring calls early in that window to leave buffer. Note the seasonal wrinkle: when Madrid is on daylight saving and Shenzhen isn't, the gap between them grows or shrinks by an hour.