Well, at least my uterus has a strong sense of timing - Fair warning, this post is seriously TMI
I have no internal clock. I need an alarm clock for everyday of my life, and I never know what time it is without consulting my watch. My theory is this is why I'm not very sensitive to jet lag - given a few external clues (sunlight, or lack thereof, a meal) I can pretty easily convince myself of any time of day.
My uterus, though, is like clockwork. For most of my life I have had very regular periods, even without birth control pills. So yesterday, at the DC airport, I was particularly annoyed to discover that I had started my period, one day early. It wasn't until I got home and looked at the calendar that it occurred to me that with all the time zone crossing my body was actually in the future and my regular cycle was just on time.