Svalbard in July has no sunset: the closest we got was on this walk late at night, when the sun disappeared behind a mountain for a while. It was pretty surreal having 24 hour daylight, and I was really thankful for the routines that shipboard life gave us (set meal times and 9am briefings stopped the days from drifting completely). But it also meant that you could easily change your schedule: I went on watch a couple of times between midnight and 4am (once to vomitous effect when we were sailing in rough seas).