srsly tho...
most nights I go to sleep sometime between 2 and 3am, and unless I have some reason to be up, I just sleep in until I wake naturally or get woken by something (a kid jumping on me, a noisy lawnmower beneath my window, the telephone, etc), which is usually around 10 or 11am. The main snag with this being that I usually do have a reason to be up, so I average around 5 or 6 hours' sleep most nights.
Not having the opportunity to nap in the daytime (and not being able to really anyway), I just soldier through and don't really notice how tired I am until things quieten down at about 7pm. But then, I feel like I need to have an evening, y'know, some time to myself? Or someone will call round (happens a lot), and by the time 11pm comes round I'm bright eyed and bushy-tailed, no matter how exhausted I felt before.
I have tried many times to get my body clock round to more sociable hours, but it can only work for as long as something's forcing me - literally, like a monastery timetable, curfew and bell for example - and even then, the longer it goes on, the more I start sitting up and reading in bed 'til 2am, even though I'm up at 6.
I remember seeing this show on TV where they documented the development of a bunch of kids all born on the same day. It showed how the 'owl' and 'lark' sleeping patterns were biologically programmed into these babies, how they each had widely varying preferred sleep patterns totally naturally, and explained it by saying how, in primitive conditions, y'know, it's logical that some people are meant to stay awake through the night to keep watch and other stuff. Really interesting.
My mom corroborates that I've always been a hardcore night owl since my infancy.
edit - HOWEVER it's only because I force myself to get to bed that I go as early as I do, cos I know I've got to be up the next morning and stuff and I don't want to fall too far behind on my sleep cos I know I never get the opportunity to catch up. On weeks when the kids have been at grandma's and stuff like that, I've happily pushed bedtime back to 5am and later and gone completely nocturnal, waking up in the early afternoon, mooching around until early evening, then coming to life around 7pm, to burn brighter and faster the later it gets. It's always hard to adjust back to the early pre-3am bedtimes...