I remember reading in Hardy's Far From the Madding Crowd that Gabriel Oak was (quote from memory warning) "of that age when people begin to stop prefixing 'man' with 'young'" - and he's then revealed to be 29. Ever since, I have thought of 29 as the age when one stops being young. That means I have nine months of youth left.
young man is fine,but i work as a cart pusher at walmart(a job usualy reserved for those under age 18), and i get called "hey kid". when i tell my coworkers how old i am they are supprised(apparently i look quite young for my age).