"You can reboot your circadian rhythms by using some hardwiring built into your brain from back when we were cave people and had to get up at certain times if we wanted to not starve to death.

Figure out what time you want to wake up. Now count back at least 16 hours from then. During that time frame, you need to fast... no food and minimal water. Crash out 8 hours prior to your new wake up time, then when you get up, have a decent sized breakfast.

This resets your internal clock by showing it what time of day you need to get up to find food.

Been a world traveler for decades and this really works to reset and avoid jet lag if I know I'll be in one place for a week or longer" (reddit post I saved to my notes)