I'm not op, but I'm 55° north.... It's 22:25 here and this is how light it is right now. In another 4 hours, it'll be nearly full daylight again!

I'm 61°N, the sun barely sets in the summer. Today, sun rises at 3:51, sets at 23:14. It's proper dark for maybe 2 hours

51° N. I'm also on the fourth floor of a building, so the horizon is farther away. I'm exaggerating a little bit. By "still up" I really mean it's still bright enough out, twilighty, that it would affect my ability to sleep. Bedroom window also faces east west, so, yeah it's a combination of factors but still.

I grew up 2 blocks from a train station that would start running routes every 10 min starting at 5:30 or so. Oh boy I can't believe I slept through it as a kid, I wouldn't be able to now without re-acclimating.