For me, morning is the ideal writing time. That is, on those days when I don't have anywhere else to be. In the morning, my house is quiet, cool and calm, and lit with that perfect "slant of light."
In the morning I am at my most productive. Mornings are wonderful, and summer mornings are the best.
By the afternoon, heat settles in my non air-conditioned house, and the coffee pot is empty, and the noise beings, and family members make demands, and phones ring and sing and beep, and then the writing becomes slow and frustrating.
Any others have a perfect time of day for writing?