Man, am I out of practice on international travel. Apparently even if you destroy your circadian rhythms, you can get them back! After nine days in Europe and 3 days back, I'm still living on CET time, going to sleep at 7pm, getting up at 2am. Arrrgh. I used to be able to get back on timezone in one day.
It's generally why I like short international trips on business...go in for 2 days, stay on CST timezone, and come back. Stay up until 10, and I'm back.