According to Wikipedia, jet lag is “a physiological condition which results from alterations to the body’s circadian rhythms resulting from rapid long-distance transmeridian (east–west or west–east) travel on high-speed aircraft”.
I can say without a doubt that I have never suffered so much from jet lag as in November 2008, when I traveled to California with my girlfriend.
The time difference between Barcelona and West Coast US is 9 hours and even though we were there for eleven days, we never got to adjust to Pacific Time: by 7 PM we were almost asleep and at 4 AM we were ready to get up and hit the streets.
Looking back, I have concluded that jet lag brought some kind of oniric atmophere to our trip. You know, walking with altered circadian rhythms around those places you have seen about a thousand times in movies and TV series is quite a surreal experience, don’t you think?