Nocturnal up to where I'm often barely functional during the day.
I do tend to have my own sleep/wake cycles and they don't really line up with 24 hours all the time. I do know that the times that I'm actually awake at night I get more stuff done than the times where I'm awake during the day and sleep at night. I just thrive more on the quiet and dark I suppose.
That, and I have a bad mood in mornings; I can't even deal with the overall business of people going to work. Oh, and don't bother me in mornings; I will hurl a pot of boiling hot coffee at you.
I kinda manage to trick my brain partially by having the shutters on the outside of the window closed pretty much when the sun is up, so I'm kinda keeping daylight out for most part. But then again; light sensitivity seems to be part of me, so I go with shades on during the day anyway. The shutters are a comfort thing as well; not gonna get a migraine in my own room on a daily basis.
In terms of being functional in society (since, yeah... most things don't operate at night) I try to plan everything in the late afternoons, and hope I'm on a somewhat regular day/night cycle and I got out of bed somewhere in the early afternoon. My brain is non-functional before noon most of the time (unless I'm still up).
The times I have actual appointments is way too much stress for me, since I have to jump through hoops to change my schedule and go against my nature. And obviously, it's still a mess when it involves some formal thing like a therapist visit or something of that nature. I mean; I'm there and expected to have a proper conversation, while all I feel like doing is sitting in a chair and drooling and laughing like an idiot...
But I've been like this since I was a kid already; school was a nightmare because of it, and my short stint when I had a job, I felt like a zombie and only have fragments of recollection of it given how much I was out of it (I might argue that my impaired functioning made me not have a job at my former employer anymore, lol). My earliest recollections of all of these issues with counselors (be it in private or in school) all ended up in them telling me "I can't see you do anything but a freelance job where you'll be able to plan your own hours".