I have found that I'm most creative and productive right after waking, but it doesn't last long. My energy levels crash some hours after waking, then slowly rise as the day turns into evening hours. At that point, I'm not as energetic as I am right after waking, but that state can last well into the night until I can't stay awake any longer. Even as I'm getting tired at night, it seems different than the crash at midday. So, I think it's true you can have a higher level of productivity in the morning for a short period, but also get more done in the evening because of the extended period of "good enough" energy. Morning people and evening people are both correct. Circumstances generally determine which of those two ends are most easily exploitable. Because I work from home, I can take advantage of both.