My dad researches and instructs other teachers on methodology and school effectiveness, including work in far-flung places, with it regularly taking him to Brazil, Pakistan, and Tonbridge Wells.* Because he is now such a seasoned traveller, he has got used to odd hours and his body clock being awry. One of my favourite ever conversations with him involved him announcing that he'd found a way to get over jetlag. Ever eager to get over it, as I suffer terribly when I don't sleep (as I may have mentioned), I asked him what it was. "Just don't give in to it. I've decided" came the response.
Would that I had the willpower. Waking up at 5 two mornings in a row seems to indicate otherwise.
* I always want to ask him if he ever comes across "angry of..." the aforementioned TW.