Strange - the date in my profile had me being more than 10 years younger than I really am! Year zero for Unix and most operating systems these days starts from Jan 1st 1970. My birthday was listed as Dec 31st 1969.
I think that I must have left my birthdate blank and the system applied some sort of default ... but if that was the case, you'd have expected load of people to have their birthday that day ... strange indeed. Maybe I'll drop Mark a PM about it.