30
The main thing that got me when I turned 30 was that suddenly, it was so easy to compare myself to the world by age using easy math.  I really noticed it when I was listening to hockey games and commentary, and the announcers would discuss players.  Some players were in their prime (24 - 27) some were veterans (28 - 32) and some were still trying to lend their leadership to teams even though they had lost a step and were near retirement (33 - 38).  When I was in my 20's, even 29, I still didn't do the math to determine my age relative to the players, in my eyes I was still 18.  Then I hit 30, and I realized that I would be a veteran, nearing my end in the league.  FTW?
Other things also made me aware like being the same age as my parents when they had me, I am in turn having Wylie at the same age as my parents.  So I am exactly as far along with my life as they were with theirs. FTW?!?!!?
While I was not bummed to turn 30, there was this strange cosmic shift in my brain about age, and relativity.  I still feel 18, I still like almost all the same crap I did when I was 18, I still know most of the same people as I did when I was 18 (weird), but I am absolutely more wise to the ways of people and the world, and my body sure as shit does not act like it did when I was 18.  At least I still get carded when I go out, sometimes.
So, welcome Jael.  It is a great club to be a part of, it is great to have reached this milestone.  With some hesitation I would say we are all officially "adults", whatever that means.  Well, not lilrudy@aol.com, but he's close on our heels, if he doesn't cut himself to sleep before he makes it!