Atlanta is 2 hours behind Brasília
Best overlap: 10:00 AM to 6:00 PM in Brasília is 8:00 AM to 4:00 PM in Atlanta.
Your shared working hours run 10:00 AM to 6:00 PM in Brasília (8:00 AM to 4:00 PM in Atlanta). The 2-hour gap barely gets in the way — you've got 8 hours of overlap, so pick whatever time fits the agenda. Just remember Atlanta changes its clocks for daylight saving and Brasília doesn't, so confirm the overlap whenever the seasons turn.