Both, unfortunately. For example, I was up at 6 am, it is now nearly 2 am, and I will be up again at 7 am. I don’t sleep worth a bean. The catch is that to feel perky, I need a mininum of 7 and preferably 8 hours of sleep.
I have Latina blood and am on that schedule. Which means I’m no good at all during siesta hours, although very lively at dawn, dusk, and way past your bedtime.
There is nothing quite like seeing a beautiful sunrise. Right before toddling off to bed. 
I had major problems in college because of the stupid 8:00 AM classes.
Given the opportunity, I stay up until 3 or 4 am, and sleep until noon. I’ve been that way all my life. I can function on a day schedule, but anyone who pays me to be at work at 8am is getting two hours a day of me pretending to be human.
My boyfriend is a day person, for the most part, but he did pretty well back when he was doing graveyard shifts.
A link that may appeal to the night owls here:
The Nocturnal Manifesto
Definitely a night owl here, though I am forced by economics (read that as job) to deal with daylight hours. My body would like it a whole lot better if I were crawling IN bed at the time I usually crawl OUT of it.
I’m an early riser, though I usually stay up until about midnight as I don’t seem to need more than six hours of sleep. I used to work 6:00 AM to 2:30 PM and I loved this shift. Then they changed it on me so I currently work 7:30 to 4:00, which is still good. Soon I’ll be going back to 6:00 to 2:30, which I’m looking forward to. I like having my work day done before most other people. I don’t work well at nights. I used to manage fast food and I’d often be there after midnight, sometimes as late as 3:00 AM. I was always tired and more than ready to go home by then. I don’t know how you night owls do it, but I know the world needs people willing to do work at such hours and I’m just glad I’m not one of those people.
Another night owl. They pay me to be here at work from 9ish to 5ish (they aren’t rigid, which is good 'cuz I actually stagger in between 9:30 and 10) and before noon about all I’m good for is reading my email and responding to help requests. Can initiate anything. By 2, though, I’m diving in, and between 3 and 6 I get a lot of work done. I’d get more done if they had me working until 10 or so but my girlfriend wouldn’t be happy, and why should the work environment get all my best hours anyhow?
PS – I thought the other folks, those weird (& occasionally disgustingly self-righteous) folks who do the “early to bed and early to rise” thing and etc., preferred to be called “Morning Larks”?
Yay vampire schedule! When I am able to sleep at all it involves me falling asleep between five and six in the morning and waking up around five or six in the afternoon. When forced to be awake during the day it throws my whole sleep schedule out of whack and it takes a sleepless day or two to get it back to the way I want it.