I understand that in team sports, you kind of have to use the year of birth. You don't want your quarterback to change category in mid year.
However in swimming, they have moved to date of birth. In age group competition 1 year makes a big difference. Having a birth date of Jan 1 vs dec 31 is huge. If you are a decent runner (does not have to be the best), it is rare that someone 1 year younger beats you. So if you are born on dec 31st, it really sucks.
Move to a date of birth system and that equalizes everything.
I think that track should do the same as swimming in this regard.