Wellington is 10 hours ahead of Johannesburg

There is no standard 8-to-6 overlap. Someone joins early or late.

Set against a 10-hour difference, Johannesburg and Wellington run their workdays on completely separate schedules. Block a single recurring off-hours slot that both teams agree on, rather than negotiating a new awkward time every week. Daylight saving complicates things slightly: Wellington observes it, Johannesburg doesn't, so the difference flexes by an hour part of the year.