N24, Non-24, or Non-24 Sleep-Wake Disorder, is a circadian rhythm disorder where your body doesn't run on a (roughly) 24-hour cycle like most people/people without the disorder itself. For example, my days run roughly 18-19 hours instead of a typical 16. My sleep gets later and later and later. I've tried melatonin, tried resetting my sleep schedule by staying up for >24 hours until a "normal" time for bed, and tried keeping ambient noise on like music or nature sounds. I've tried blue light filters. My days are just 26-27 hours instead of a normal 24, though every person with N24 is different.

It's primarily diagnosed in Blind patients, since the cause among Blind people with the disorder seems to be that not being able to see the transition from day to night makes their bodies not produce the proper sleep hormones at the right time.

Among sighted people, the cause seems to be unknown (last time I checked; just one person with the disorder should not be your only source of information!) and, since N24 among sighted people is more rare and less lucrative, it's an orphan disorder. There's not much research into how to help us sighted people with N24 because treatment is often pricey or not an actual solution, or it is aimed directly towards helping Blind people with N24.

As far as I know, there's apparently an implantable device in development. The main suggestions I see are training via sun lamps and melatonin or just trying to get on sleeping pills by lying about insomnia. There is a pill that can be taken, but if you live in the US, it is extremely expensive. So, essentially, this orphan disorder is overlooked and misdiagnosed, and those of us with it have to hope that one of the coin-toss methods of treating N24 works.

N24, even on its own, can be a very disabling disorder. You're either too-sleep deprived to do the things during the day you need to or are busy being asleep because the human body needs rest at some point. Socialization gets very difficult when your circadian rhythm is nocturnal for a couple of weeks. It's an isolating experience. It also makes it harder for people to work and make themselves money. I don't even know if N24 is something that can apply to an application for disability, though given it's not well-known, I doubt it is.