Natural light can cure jet lag? Studies on seasonal affect
disorder and on circadian rhythms yielded this useful information
for traveling divers: Jet lag can be cured, or your
body re-set, simply by using full-spectrum light. It has been
codified into something like a slide rule (a free download at
  www.bodyclock.com), and depends on your preferred
wake-up time and the number of time zones you're traveling
east or west. 
When you get on the plane, set your watch to destination
  time, and from that point on, follow the schedule of exposure
  to three hours of full-spectrum light, followed by three hours
  of no light. On a long trip, say New York to Hong Kong, it
  means that you need to have full-spectrum light entering
  your eyes at a time when the cabin is dark. In pre-9/11 days,
  I would ask if I could sit with the pilots, who were happy to
  have company. Now you need mechanical help.
I use a full-spectrum light visor that makes me look a
little like Geordi La Forge from Star Trek: Next Generation, but
I'd rather look spacey than feel lousy. During the blocks of
no light, I wear a super-dark visor. Trips with more than six
or seven time zones crossed require a second day of following
the light exposure rules. I buy my light visors from BioBrite
(www.biobrite.com), and have used them for years. Even
after trips crossing 12 time zones east or west, I have been
ready to dive on the second day. The Jet Lag Visor is $299,
but worth it.
For me, the real test is the gut - - not a gut feeling, but
  what your gut does, if you get my drift. Using light therapy, I
  stay on schedule. What my dive buddy and I love about the
  system is first, it really works, and second, there are no drugs
  involved. I have given my jet lag kit to a colleague who traveled
  to Tokyo, Paris, then India for a series of talks, and he
  couldn't believe it. This system really works, folks.
 - - Mel McCombie