I think the race age depends on the tri. The official USAT rule is that your race age for 2006 is your age as of 12/31/2006. I recently did my first tri (Chattanooga Waterfront tri) and they followed that rule. But, I'm sure there are many races that are like the one Brina did that just go with your age on the day of the race.

I'm in the middle of an age group (I'm 42) and my birthday was early enough in the year that my race age was my actual age. I'm not sure I'd want to be bumped into a higher age group based on this race age rule even if it meant I might place better in my age group. I guess I have a couple of years before I have to worry about that.