The correct answer is "it depends" as there's a dependency on the latitude you are at. Places exactly on the equator have days of constant length throughout the year. Also, if you were at the north pole, for some time of the year there would be no sunrise or sunset at all. So you could say that each day was equally long (or each night equally long in the winter!) during the summer... namely 24 hours. In the winter, you'd have days where the sun didn't rise at all, so then you could say each night was 24 hours.