In addition, there is a notion of "photometric nights" which include, among other requirements, Sun being at least 24 degrees under the horizon. These conditions are necessary to conduct precise photometry, because an extremely tiny amount of scattered sunlight still makes it through when sun is between 18 and 24 degrees. So in a way, we can add "photometric twilight" to the list, although the number of people who are affected worldwide will probably fit into one big room.

A very big room, with me in it ;)

I made a web app that shows twilight times: https://sunclock.net

Also shows sunrise and sunset times, and moon position and phase.

Exceptionally cool, thanks! I was about to ask if anyone had app recommendations but I just added your site as a PWA. Works great!

I love the daylight chart they use on this site.

https://www.timeanddate.com/sun/usa/utqiagvik

(Scroll down for 2022 Sun Graph for Utqiaġvik)

Yes, I love that sun graph as well. I keep hoping to find an open source mobile app that has something like that.

Currently I use Suntimes (https://github.com/forrestguice/SuntimesWidget/releases) and the only thing I feel is missing is one of those sun graphs. I'd contribute one myself but I feel like it's a bit outside my wheelhouse at the moment.

Some trivia make people more interested in you. This one will actually probably lose you friends, if my experience is any indicator

You may be generally right but you don’t speak for me! ;)

I read this and sincerely thought “wow, I haven’t ever given much thought to the intricacies of twilight but it’s really interesting!” Then again it’s around this time of year I start to regularly visit the site posting this article, and I’m not so much concerned with making more friends.

In my experience people think it's helpful sometimes, because they know that sunset doesn't mean the light suddenly disappears, but don't know how to act on that more predictably. So if you're doing something with people outdoors around twilight, and people are wondering exactly how much light there will be at different times, bringing it up is a good thing.

install the 'suntimes' app from fdroid and never get bored telling people which sunset is when, or what time it really is

moon stuff too! it's gibbous you know

Tiffany knew it was gibbous because she’d read in the Almanack that gibbous meant what the moon looked like when it was just a bit fatter than half full, and so she made a point of paying attention to it around those times just so that she could say to herself: “Ah, I see the moon’s very gibbous tonight . . .”

It’s possible that this tells you more about Tiffany than she would want you to know.

I count 4 types, 5 if you consider Breaking Dawn parts 1 and 2 as separate.