I just crossed my mind while reading about people flying at night. Here in sweden in the summer especially mid summer that sun dose not go down so we have sunlight all the time. But in winter it is the opposite and it gets to the point where we have 2 hours of sunlight a day. So like 2.30pm it can be pitchblack. So the question is the night flying law. Is it based on time or the amount of light here is or something else.