I wonder how this maps (if at all) to Ayurvedic cycles [1]? This one is quite curiuos:

    Mid-night – 10pm-2am is again pitta time. 
    The fire element is strong, and the stars shine brightly. 
    Although pitta will give a spurt of energy and creativity one must avoid staying up into the late hours. 
    If one stays awake until after after 10 pm, the 
    active nature of pitta can prevent sleep. 
    It is the hours of sleep that one gets before 
    midnight that are the most rejuvenating.

[1] http://flowingfree.org/using-ayurvedic-principles-to-live-in...