Well, I live about 800 km from the Arctic Circle, it is mid-July and the Sun sets at about 2200 today and rises at about 04:00. Roughly 6 hours without Sun. Compass works fine here.
At a place that is located at the Arctic Circle, the Sun sets at 23:19 and rises at 02:09. Just to give some idea of how the lighting is /out there. Compass works fine around that place too.