Johannesburg is 10 hours behind Wellington

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

Wellington and Johannesburg are 10 hours apart, and that gap is wide enough that their normal 9-to-5 workdays never quite touch. If you meet regularly, fix one off-hours slot and rotate it between Wellington and Johannesburg so the burden doesn't fall on one team. These times hold for most of the year, but Wellington's daylight saving (which Johannesburg doesn't use) shifts them by an hour twice annually.