When I was a younger person (from about age 14 - 25) I simply could not get to sleep before 2 or 3 in the morning, and would sleep late - until noon if I could get away with it. That didn't go over well during school terms, though. I'd be a walking zombie in classes. I had to be up by 6:00 and out the door by 6:30, but I still could not get to sleep before 2:00am. Had nothing to do with TV (didn't have one) or caffeine (didn't drink it).
When I was in grad school in my 30s, after spending several years in the workforce working night shifts (which was great, by the way), I spent my most productive time from 10:00pm - 4:00am. I had a toddler in tow, but she adapted a bit to my schedule.(Finding a daycare that would take her for anything other than 8:00am- 6:00pm was quite a challenge, though.)
Now, after having spent 20 more years working in 8-5:00 jobs I wake up early on the weekends, just as if they were weekdays. But on holidays, any time more than a week, my internal clock tries to re-adjust. I find my self awake later and later, and sleeping later. Everything shifts - I had one year where I was staying up until 4 or 5am again, and sleeping til 1 or 2 in the afternoon. It was great - except for the first day I had to be back at work at 8:00am! Given all that, I think I must have been designed to be more nocturnal than a day-worker.
Other than that, the only sleep oddity I have is that I can sleep anywhere at any time. As long as I'm not worried about having my purse stolen, for example, I can nod off for 10 minutes on a park bench, if I choose. I've been able to do that since I was in my 20s (possibly earlier, I just don't remember anymore) - I just switch the world off.