Duncan MacLeod wrote:
Maybe this will help ...
2249 - Age 17 - With the backing of Commodore Mallory, James T. Kirk, second son of the late Commander George Kirk, enters Starfleet Academy at the youngest age allowed.
Do we know for sure that this is the youngest age allowed in Kirk's time? I don't recall exactly, but I'm sure TNG said something of the Academy entrence age, though that took place more than a century after Kirk's time at the academy. The--non-canon, of course--TWOK novelization mentions 14 year old midshipmen, which could put a few more years in there for Kirk's career.
"Canon is only important to certain people because they have to cling to their knowledge of the minutiae. Open your mind! Be a Star Trek fan and open your mind and say, 'Where does Star Trek want to take me now'." - Leonard Nimoy