Our bodies are biochemically coordinated with the daily rhythms of the sun. This coordination system is called the “circadian clock”. Jet travel, either East or West, (but not North or South) can quickly place us into a new time zone that confuses our circadian clock, and make it difficult to sleep at night, despite our exhaustion from travel, and make us tired during the daytime. The effect can last for days, until our circadian clocks are reset to the new time zone. Medication can accelerate the rate at which we adjust.