Portland is 10 hours behind Johannesburg
There is no standard 8-to-6 overlap. Someone joins early or late.
Coordinating Johannesburg and Portland is tricky: 10 hours of separation means their standard hours don't intersect. Async-first is your friend here. Reserve real-time meetings for the rare occasions someone can log on before or after hours. Because only Portland changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Portland enters or leaves daylight saving.