Geneva is 6 hours behind Hanoi
Best overlap: 2:00 PM to 6:00 PM in Hanoi is 8:00 AM to 12:00 PM in Geneva.
Plan around 2:00 PM to 6:00 PM in Hanoi, which is 8:00 AM to 12:00 PM in Geneva, to catch everyone during office hours. Since Geneva is 6 hours behind Hanoi, the workdays overlap by around 4 hours; 2:00 PM in Hanoi (8:00 AM in Geneva) makes a reliable recurring slot. Seasonal note: Geneva uses daylight saving and Hanoi doesn't, so double-check the times in your own months — they can move by an hour.