This is highly geographically dependent. For example, in Berlin where I live currently, sunrise in mid Summer is at 4:40am. I'm highly sensitive to light, and u

This is highly geographically dependent. For example, in Berlin where I live currently, sunrise in mid Summer is at 4:40am. I'm highly sensitive to light, and use blackout currently for this reason. That's not a remotely practical wakeup time with a regular work schedule.