Reykjavik is 1 hour behind Budapest
Best overlap: 9:00 AM to 6:00 PM in Budapest is 8:00 AM to 5:00 PM in Reykjavik.
The overlap falls at 9:00 AM to 6:00 PM in Budapest, or 8:00 AM to 5:00 PM if you're in Reykjavik. Reykjavik is 1 hour behind Budapest, and with 9 hours of overlap you can even run back-to-back calls without stepping outside business hours. Because only Budapest changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Budapest enters or leaves daylight saving.