I guess jet lag would distress most of the people who occasionally travel long distance across wide time zones, for the different time would disturb your circadian system that your body had long got used to.  The "symptom" would take couple days for you to get back to normal, and sometime it would prolong to a week or so. 

I have no problem in adjusting my bed time, but I do have some other problems that trouble me a lot, e.g. bowel movement.