Not all of it is without choice. I used to be a night owl. I woke around 10am, worked from 11am until 1am or sometimes later. The invariant was that I generally

Not all of it is without choice. I used to be a night owl. I woke around 10am, worked from 11am until 1am or sometimes later. The invariant was that I generally slept between 9-10 hours. I also suffered from seasonal affective disorder and winter time depression with short days in Canada. To help with this I started spending time outside during the early part of the day and generally ate my lunch outside if possible. This helped somewhat. This switch to prioritizing sunlight exposure also made me consider that sleeping while the sun was up and working in the dark was a strange choice. For more than the last 25 years I've intentionally time shifted to ensure that I don't waste daylight hours sleeping. If I'd follow my natural sleep rhythms I'd almost surely drift later, I'd we waking several hours after sunrise and working in to the evening. Even though I have to have some discipline about using an alarm clock and only allowing myself 1 day a week to wake naturally it is not actually that hard because I do it consistently. I could also easily stay up late one night, but getting up at the same time every day makes staying up harder. My intentional time shifting isn't that dramatic of a "hacking" of my natural inclination. It has made a difference with seasonal depression and I've found that social activity works better with a time schedule aligned to daylight hours. It is easy to read a study like this and conclude that personal choice plays no part in determining your "fate". You have some flexibility and choice to do what you need to do. An inclination is not an outcome.