This line made me think a little.
Is "younger than my age" an arbitrary construction? When I was younger, my grandparents (admittedly from "the old countr(ies)") dressed differently than younger people. Now I and my peers, grandparents ourselves though just a few years younger than my grandparents were as I remember them, wear blue jeans and Crocs and athletic shoes and yoga suits just like people in their 20s and 30s and 40s.
My grandparents listened to different music than they did when they themselves were younger. People my generation are still listening to the music they listened to growing up and the songs and movies and books of our early adult years have become part of omnipresent mass culture much more so than the entertainment of my grandparents. And people my age listen to Bruno Mars and Taylor Swift and Adele in a significant measure compared to the much younger core music-listening populace (all North American, I grant you, but...).
Certainly there are fashions that look better on younger bodies than mine. Surely there are musical trends today that seem as foreign to me as New Wave/punk was to my parents and rock and roll was to theirs. There absolutely is ageism in America, particularly in some cultures. But is acting or dressing "younger" than our age a shifting standard?