Depending on the latitude of the area they are in (and since this was filmed in summer) the higher north you are the longer you have daylight.
As someone who had lived 26 years in Alaska, during summer while we do have sunset (at least in most of the state), we for the July and August often have enough light throughout the whole night (ie sun as set, but its so close to the horizen that it never truely gets dark).
Of course for winter the reverse is true where we would only get 4-6 hours of sunlight (and if you had a day job without windows you went without seeing the sun) and of course even further north they go literally without the sun rising.