I am most productive and creative at night. Dunno why but I can't sleep at night. Too much energy and overflowing with creativity! (Anyone feels the same?)
Most productive? From about 9pm until about 6-7am. That is, if left entirely to my own devices. Having to work a day job during the week, I can't keep those hours... so I wind up getting most of my meaningful stuff done between about 8pm - 11pm or so.
All day! If I can, I try to only set timers for 8 hours. Not that I always sleep 8 hours, just that I goto bed whenever I'm tired, and wakeup when I'm well rested. The rest of the time I work.
That being said, I also take a day off, an afternoon off, etc. just to keep myself from burning out.
Some people don't work well in a routine manner. Startups are so dynamic too, so if you're in that realm of things, it's almost impossible to have a routine schedule.
Going to bed every night, knowing you won't have to wakeup for 8 hours, is really comforting. I usually wakeup before my timer goes off, but it's way better sleep.
Unfortunately this can't always happen, especially with meetings and such.
I'm normally most productive between 10am and 4pm. I then get better from around 530 till 730 (but that tends to be that people stop calling me or dragging me into meetings).
On the weekend I tend to be most productive between 9am and 12pm (if the wife's still in bed), but I don't really gear up till between 2pm and 7pm.
My most productive time is usually after lunch as my mornings are usually filled with meetings, phone calls and emails. Evenings I work on my own projects and freelance. I'm more enthused about the work but find there are more distractions as well.
I tend to work weird hours 2am-8pm. During this time my colleague tends to be less sociable or asleep. I like them but i tend to work better without any scrutiny.
I am with you, though mine is from 9AM-12:30PM. Once I come back from lunch, all bets are off. That is the time people start coming in with tickets, etc.
Night as in 10pm-3am