Ken Wright of the University of Colorado Boulder said a small study indicated a way to reset the body's internal clocks is to go camping and not use artificial light.
The Colorado researchers took eight healthy young adults back country camping for a week in the Rockies, where they had no light at night other than a campfire.
Before camping, they typically slept around 8 hours, starting after midnight:
"The study subjects obtained the same amount of sleep while camping, although it was timed a little more than an hour earlier -- so bedtimes were earlier and wake times were earlier," Wright said in a statement.
For those who cannot go camping, Wright suggested more morning sun -- wake early and take a walk outside to get a good dose of natural light -- and use less evening electric light to reset your body's inner clock.
The study was published in the journal Current Biology.