I find I can get so much done between midnight and 4 a.m. Everything is quiet, no one is disturbing me, and if I go to bed then, I just lie awake thinking of ideas. They are very creative hours for me. One night a week I crash out, though.
A really good day for me is to write my book for about four hours, go to the writing room for about four hours and then maybe come back to the book to finish the day for a few more hours of it.
I do my best writing between 10 p.m. and 5 a.m.. Almost every friend I have who is a consistently productive writer, does their best writing between 10 p.m. and 8 a.m. My quota is two crappy pages per day. I keep it really low so I'm not so intimidated that I never get started. I will do the gathering of interviews and research throughout the day. I'll get all my notes and materials together and then I'll do the synthesis between 10 p.m. to bed, which is usually 4 or 5 a.m.
Writers tend to work early in the morning, or late at night, when brains are naturally able to focus deeply on one thought. In the middle of the day, distractions are unavoidable. I wonder if anything worthwhile has ever been written in the afternoon.
As long as I can stay creative and used my mind, it can be 20 hours a day. I sleep four hours, so I've got 20 hours.
Most writers seem to prefer the morning, or they feel at their best in the morning. Ideas are popping into your head while you're in the shower. And that's true for me, as well.
My day starts at 5 A.M. and gets over at 10:30 P.M. Its a long day but I love it... I can't sit idle.
I have a studio at home, and do 3 hours a day that way.