Rio de Janeiro is 4 hours behind Geneva
Best overlap: 12:00 PM to 6:00 PM in Geneva is 8:00 AM to 2:00 PM in Rio de Janeiro.
Plan around 12:00 PM to 6:00 PM in Geneva, which is 8:00 AM to 2:00 PM in Rio de Janeiro, to catch everyone during office hours. That's a roomy 6 hours of common time each day, so finding a slot that suits everyone is rarely a problem. Daylight saving complicates things slightly: Geneva observes it, Rio de Janeiro doesn't, so the difference flexes by an hour part of the year.