There are so many variables here. Personal inclination vs commitments which HAVE to be.
A lot depends on the length of daylight hours. In the winter, the sun comes up (or seems to come up) around 8 am and sets around 4:30 pm. In the summer, the sun is up around 5 am and sets around 9:30 pm (or so it seems). Since I seem to be more in the flow of the natural seasons, that has an effect on how I feel at different times of the day. It's not so much 'clock-time' as hours of daylight and hours of dark. Right now, close to the winter solstice, we have a lot of hours of dark! And it's colder, too, which has an effect on how I feel and how much energy I have to be doing what I have to do.
Also, in the summer time, there is more daylight! Yay for daylight! Sunshine! At those times, when it is sunny out, all kinds of enthusiasm for getting up and doing things abounds.
That said, I notice a huge tendency on my part to turn into a night person and want to sleep in in the morning. However, since I have commitments which start in the morning and continue through the day, that doesn't seem to happen.
Maybe one day, I'll find out how it is to be a night owl being a night owl. I think that would be great. But in the meantime ... give me coffee ...