This is a linkpost for https://medium.com/@owenshen/the-ancient-god-who-rules-high-school-e0645b100ae6
Anyone can adjust their circadian rhythm by just going to sleep earlier,
No, the circadian rhythm doesn't work that way. Perhaps you don't notice because your chronotype is earlier than your lifestyle required so you never had much trouble falling asleep even when going to bed relatively early, but people with later chronotypes if they go to bed earlier will just take more time to fall asleep.
Everyone has trouble falling asleep when they're going to bed earlier than usual, at first. If you keep at it and are consistent about avoiding things like bright artificial lights, high general arousal, strong drugs like coffee and other adverse environmental cues later in the day, you'll fall asleep and your "chronotype" will shift back as intended.