For me, it's realllllly early in the morning. I used to get up at 4 a.m., grab a steaming cup of coffee, and just start writing. At that time of day, words flowed so easily that I could finish a 1,500-word post in an hour. Later in the day, that same post would've taken me twice as long.
But that's not the case for everyone. Some people prefer working late into the night. Others hit their stride after lunch.