For those of you who want to calculate their own rollover day, first take your base number, which is 9855 (365*27). Then add the number of leap years that are between your birth and your 27th birthday. If you were born on a leap year but after February 29, or the year after a leap year before March 1, this number will be 6. Otherwise, it will be 7. Add this to your base, then subtract the whole from 10,000 (you should get either 138 or 139). Now pull out a calendar and count that many days past your 27th birthday. That day marks your 10,000 day rollover.
Jen, your rollover day happens on December 22, right around the Solstice. How cool is that?
Edit: Now that I've done all the work by hand, I come to find that someone's already made a calculator for it: http://paulm.com/toys/10k-day/index.html He calls it 10k Day. I prefer Rollover.