Reykjavik is 1 hour behind Madrid
Best overlap: 9:00 AM to 6:00 PM in Madrid is 8:00 AM to 5:00 PM in Reykjavik.
Target 9:00 AM to 6:00 PM in Madrid, which lands at 8:00 AM to 5:00 PM for the Reykjavik side. Reykjavik is 1 hour behind Madrid, but you'd hardly notice — 9 hours of shared hours makes this feel like working in neighbouring time zones. Note that Madrid follows daylight saving while Reykjavik stays put, so the times above drift by an hour seasonally.