Shanghai is 8 hours ahead of Reykjavik
Best overlap: 8:00 AM to 10:00 AM in Reykjavik is 4:00 PM to 6:00 PM in Shanghai.
Aim for 8:00 AM to 10:00 AM Reykjavik time — that's 4:00 PM to 6:00 PM over in Shanghai. Shanghai is 8 hours ahead of Reykjavik, so you only get about 2 hours of overlap a day — worth locking in a standing time like 8:00 AM in Reykjavik (4:00 PM in Shanghai) before it slips.