Today Talk of the Nation on National Public Radio had a segment on time. You can listen to it here: http://www.npr.org/2011/06/23/137372834/time-is-constant-but-how-we-perceive-it-varies (It is a half hour.) They said that before people had clocks, the went to bed at dusk. They slept for several hours, got up around midnight, puttered around for a while, then went back to bed. They referred to this a first sleep and second sleep. Those of you who wake up in the night, might try getting up for an hour or two then going back to bed. I assume you would want to keep the lights low (think candle or kerosene lamp), stay away from the TV and computer, and not do anything too waking.