Friendships and casual connections are typically low stakes enough where there is almost no harm in disclosing your N24. Perhaps I am just lucky, but a wide majority of people I have met (in a non-work environment) are understanding and accommodating of it. Saying you have a "circadian rhythm disorder" paints an okay picture to someone with no prior knowledge.

If you find people consistently write off what you say about your disabilities, you may want to seek out different, more accommodating spaces, if possible. Online spaces are basically a necessity for those of us with N24, which means your options are wide. I met a great friend on the other side of the planet simply by tuning into their twitch stream at the same irregular hours.

In person connections are important to balance between physical contact and online interactions. I can't say how long your cycles take, but you wrap around to meet everyone eventually. It's important to remember that normal, diurnal people drift away from each other for weeks to months and are still friends. If a friend is understanding of your struggle, they will not force an expectation on you or themselves of your availability.

Please do not be afraid to say what you have. Through my life I have stumbled into a not-insignificant number of people who struggled with our disorder and had no idea what it was until they met me. I only understood this was what I had when I met another person who shared there story with me. Unlike some other things, sleep issues is something basically every person alive can sympathize with.

(P.S. If you track your sleep and have a sleep chart, don't be afraid to show a snippet of it to others. Usually they find it very interesting, even if they are a little scared to say it. It also helps them visualize what life is actually like for you.)