Nicholas Alexander BuckendorfWhile there is some truth about the
  circadian rhythms regarding sleep patterns, amount of light -
  and that it is possible to adjust rhythms somewhat based on
  artificlal light and sleep changes - as somebody who has changed
  his own sleep patterns drastically over the past year in order
  to get more time to work on projects (my goal was to get two
  days in one,which has wo...rked SOMEWHAT) - the "pull" of the
  2-o'clock tired is stronger than even an adjusted sleep pattern.
  "