Rio de Janeiro is 4 hours behind Hamburg
Best overlap: 12:00 PM to 6:00 PM in Hamburg is 8:00 AM to 2:00 PM in Rio de Janeiro.
For a call that suits both sides, look at 12:00 PM to 6:00 PM in Hamburg / 8:00 AM to 2:00 PM in Rio de Janeiro. Despite the 4-hour difference, a 6-hour overlap keeps things simple and gives both teams breathing room. Remember that Hamburg shifts for daylight saving and Rio de Janeiro doesn't, so recalculate the overlap after each clock change.