Jet lag, the bane of east-west, long distance travel, operates on a simple rule of thumb. For each time zone crossed, the body takes one day to recover, meaning that a routine flight from Washington to Paris can leave travelers out of sorts for almost a week.

But recent work by researchers at the University of California at Davis suggests there may be a simple solution: sunlight.According to their research, a traveler exposed to three to six hours of direct sunlight in each of the first two days after arrival can recover almost completely from jet lag.

"The cuing mechanism for the body's metabolism seems to be exposure to light," said U.C.-Davis psychiatrist Joe Tupin.

It is thought that the body has a natural 25-hour cycle that is reset each day by exposure to sunlight.