That's not necessarily true - it's age dependent. Adolescents/teenagers are "hardwired" to stay up later[1] and sleep in later (relative to adults or younger children).

1 - https://www.nationwidechildrens.org/specialties/sleep-disord...

Somehow, hardwired time to sleep is independent of sunsent and location in timezone. No matter where the sun is at, no matter anything.

In winter, there is dark at like 17:00. How do their bodies know difference between 22:00 and 24:00?

Yep, my bedtime was 8pm growing up, until middle school, then it was 9pm. 15-16 was when I stopped having a bedtime. I absolutely hated it at the time, especially in the summer because it would still be light out when I went to bed, and I never felt like I never ever felt like tired or like I needed to go to sleep at "bedtime".

In retrospect I'm glad I always had a full night's sleep, because I wouldn't have if left to my own devices.

Nowadays parents keep their kids up all hours of the night, I really don't get it. I see elementary aged kids out and about (in public) 9, 10, even 11pm.

I had similar experience. I had regular bedtime out of necessity. At the time, I was ambivalent to it and a bit jealous over friends who went to sleep whenever. They regularly went to slep very late due to watching movies out gaming.

Now in retrospective, I am glad I learned to cut activities and go to sleep. Paid off in college, actually. And I plan to do the same for my kids.

This is an overly simplistic take. Everyone has different natural circadian rhythms and not everyone is tired enough to fall asleep at 8pm.

This whole thread is a simplistic take, mostly in the other direction. When I was a teenager I woke up at the crack of dawn. And given the number of bright eyed fellow students in the same 'early bird' classes, I was hardly the only one.

Sure if humans where robots that have an push to sleep button directly when you get to bed.

My children all go to bed at 8:30 PM and only one of them naturally wakes up before 7AM.

Then they're home at 4pm and get a whole 4 hours for homework, recreational activities and relaxing.

Amount of free time is orthogonal to start time. That's controlled by the length of their school day; not when they start.