I'll say this for South Florida....

...where I have (intentionally) spent very little of my previous life but where I have been, for oddball reporting reasons, these last couple of days:

Being in the San Francisco Bay area makes me feel old, since everyone else is 25.

Being in the Boca Raton area makes me feel young, since...

Pretty soon I'll be back in Beijing, where I'll have no time to fritter away on such thoughts, since like everyone else I'll mainly be concentrating on surviving the next traffic jam or "mist" event that would be called deathly smog elsewhere. I am weirdly beginning to miss the focus-on-the-now such daily challenges educe. Rather than "old" or "young," it makes me feel... engaged.