Oooo since you read it on the internet, it must be true. Thats the time it drops below the flat horizon, but it drops below the mountains over an hour before that, which is when it gets dark. You are simply incorrect.

Unless you're above the Arctic circle, it's never perpetually dark

No chance, I live in Ketchikan and the sun sets at 3:30. We're still a month from the winter solstice, and Anchorage is significantly further north. Sunrise may be at 10 for them, but sunset would have to be 3ish