Melbourne is 8 hours ahead of Johannesburg
Best overlap: 8:00 AM to 10:00 AM in Johannesburg is 4:00 PM to 6:00 PM in Melbourne.
Keep meetings inside 8:00 AM to 10:00 AM in Johannesburg — that maps to 4:00 PM to 6:00 PM in Melbourne. Since Melbourne is 8 hours ahead of Johannesburg, the overlap is narrow (about 2 hours); a single, well-protected slot beats hunting for time each week. Finally, Melbourne observes daylight saving and Johannesburg doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.