Im sorry Mike i didnt mention it was AAU track & field that uses the 12 month age groups. I for one dont really care for the 24 month age groups, but we will suck it up, it works, for the simple fact the the 10U, 12U and especially the 14U there is a HUGE physical growth difference in some of those kids, There for a 12 month age group would really be fair, but WAY more time consuming for a tournament. so again the best way time wise is the 24 month age groups. Like i said though anyway its twisted and turned someone is on the edge. My son runs AAU track and is born Dec. 31 so he is the absolute youngest in his age group. it works out very good.