I live at 60 degrees Northern latitude, and I sleep a lot more in the winter. And it's really difficult in the summer too, because it never gets dark and you need to go to bed to get up in the morning.

For some reason it's not difficult for me to sleep past sunrise, but very hard to go to bed before sunset or wake before sunrise. And some people are the opposite.

This just applies to adults. Children and teenagers naturally sleep longer than adults and probably slept throughout the night. Plus, apparently people didn't all get up at the same time during the night. Some would be up from midnight-2am, others from 2am-4am, etc.