Johannesburg is 7 hours ahead of Atlanta during US summer (EDT), and 6 hours ahead during winter (EST). When it's 9:00 AM in Atlanta, it's 3:00 PM or 4:00 PM in Johannesburg.
South Africa uses SAST (UTC+2) year-round and doesn't observe DST.
Optimal window: 8:00 AM - 10:00 AM Atlanta time (3:00 PM - 5:00 PM Johannesburg). Morning calls from Atlanta catch afternoon business hours in Johannesburg.
Delta operates the only nonstop flight from the US to South Africa, connecting Atlanta and Johannesburg.