Reykjavik is 13 hours behind Wellington
There is no standard 8-to-6 overlap. Someone joins early or late.
Set against a 13-hour difference, Wellington and Reykjavik 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. For part of the year the maths changes: Wellington observes daylight saving, Reykjavik does not, shifting the overlap by an hour.