everything's smelling like roses

So here is a question for you all out there...I had to wake up extremely early to finish a bit of homework (a rather large bit of homework, actually). And as I sit here, with it still dark outside, my cup of coffee and my mouth apparently wanting to catch some sort of insect, I wonder about in the HP books, when they wake up early to finish homework....how do they do it without an alarm clock? I'm not even going to touch the question of how do they get alert enough to do the work without coffee, but seriously, no alarm clocks? How on earth do they do it!