It is quite logical, the night is much longer and we used to depend on the light cycle. Also many animals hibernate in the winter, we just sleep a bit more, it

It is quite logical, the night is much longer and we used to depend on the light cycle. Also many animals hibernate in the winter, we just sleep a bit more, it is an adaptation to environmental conditions: less light, less food, movement in lower temperatures require more energy, sleep conserves energy. In my country we have a bit less than 9 hours of light in December and over 15 hours in June, we continuously adjust for it.