I'm thinking on the colonizing of another planet by humans. The conditions of this planet are quite different from Earth, and particularly the day-night cycle is much larger.
In my fictional planet, the day will last 48 hours. The day-time and the night-time is duplicated, and that means than the proportion between the hours of sunlight and the hours of night is the same than in the Earth.
Would the humans living on this planet adapt their sleeping to the new day-nigth cycle, i.e., will they sleep during all night-time and be awaken during day-time? (This is after some years or even, if needed, a couple of generations.)