I don't know about the scientific, biological best time, but in Florida, it's got to be morning! It's cooler, and it doesn't rain. I've given up competing with the heat in the afternoon. I add miles to my morning commutes, and limp home in the afternoons.

An hour a day is a great base, but you need a long ride every week, too, right? You should be slowly adding on 10 percent to the long ride every week, until you get to 50 or 60 before the century.