I second this.

Personally I am super productive from about 9pm to 2-3am.

But I need to be at the client at a reasonable hour (9am-9:30am).

Lately I've taken to hacking away from about 9pm to midnight then going to bed so that I can keep everyone happy. Of course, I tend to toss and turn a bit because there is always something that my mind is chewing on that I left off at midnight.

Weekends, all bets are off and my sleep schedule gets totally messed up with late nights and early mornings (2 year old kid). Ugh, I am not 18 any more :)