I swear that you just come pre-programed. I've always been a night person. No matter how dead-tired I am all day, around 9pm or so I start to gain a momentum and can be more productive then than I was all day. I can easily keep going until 1 or later if I don't allow myself to look at the clock. And then it's the same cycle - either sleep in or have to drag myself out of bed at 7 if I have something I have to do. Thankfully ds is also a night person, so he rarely disturbs me if I do get to sleep in - he's also sleeping.