Reykjavik is 2 hours behind Johannesburg
Best overlap: 10:00 AM to 6:00 PM in Johannesburg is 8:00 AM to 4:00 PM in Reykjavik.
10:00 AM to 6:00 PM in Johannesburg is when Reykjavik is also working, at 8:00 AM to 4:00 PM their time. Scheduling is forgiving here: with 8 hours of overlap, a missed slot just means picking another one the same day.