Oh, I’m noy denying that I’m old, just that I’m an adult. 
Along that line of yours, I was on accuradio looking for the 80s channel and it’s listed under Oldies!!??!! :eek:
Regularly scheduled prostate exams.
Lots of little incremental changes, but I think adulthood was achieved when I bought a washer and dryer, and suddenly for the first time in 20 years I did not have to hoard quarters and plan 3 hours of laundramat time every week.
I still get those weird moments of being in the middle of some every day chore, like washing the dishes, and getting a strong feeling that I’m just playing house. It’s probably my inner 'tween wanting to blow the mortgage on cheap wine and expensive men.
Having more dead relatives than living ones.
Being called “Mr. Jon” by students who don’t mean it facetiously (MAN I hate that- I think now I know why some northern women hate being called ma’am)
The realization a few years ago than I could legally marry a woman half my age in any state of the Union with parental consent, and then a few years later realizing I no longer needed parental consent.
Seeing an actuarial table of life insurance premiums and noticing how much more expensive mine are than they used to be.
Asking about dental and pharmaceutical insurance on job interviews.
Knowing I’m the only person who can remember the Bicentennial in most groups.
Realizing one day that I have a preference of prescription bottles (CVS’s over RiteAids).
When a friend died of a heart attack this summer. He was 33. I realized that one of my responsibilities to my family was to get healthy again and stay that way.
Also, when I realized during a party that my friends’ kids were sitting upstairs, playing at the landing, just like I used to when my mom entertained. I realized that my son would probably be doing the exact same thing in a year or two, wondering when the heck all mom and dad’s old codger friends would leave so he could come out and score some sweets.
Oh, yeah, and when my son vomited all over me Friday morning and, instead of freaking out, I just stood up and calmly went to the bathroom, sat down on the floor and rubbed his back and whispered to him until he was done and we were both covered in barf (he’s 19 months and doesn’t get putting his head over the toilet - nope, he wants to cling to mommy. Ick.). Even worse, I actually think it’s kind of funny now when I think about it.
It wasn’t when I signed the mortgage - still felt like playing house.
Sort of when the toilet backed up and I called my mom and she said, “Why are you calling me? Do you want the plumber’s number?” and it turned out to be a 77 year old sewer pipe that was no longer exactly there in any concrete sense, and my home warranty didn’t pay for it at all.
But when it really drove home was when I was trying to be cheap with the heat because the windows are the same age the sewer line was, and I was cold one night and I got up and said, “Damn it, it’s my house and my thermostat and I am an adult and I will turn it up if I feel like it!” and then I got to the thermostat and I realized “It’s my house and my mortgage and I am an adult and have to pay this bill” and I turned it down more and put some socks on.
I just said the other day that I feel like an adult because I had ice cream for breakfast and nobody could tell me “no”.
But compared to some of the other replies that sounds really lame now. So I’ll say: When I bought a house - about a month and a half ago. (And about a month ago realized I could eat ice cream for breakfast and nobody could tell me “no”.)
Buying a house. That I was able to go through the entire process all by myself, from looking at available homes to obtaining the mortgage, and that the bank was willing to lend me what I consider an ungodly amount of money meant that at least somebody considers me grown up.
Also, when I realized that if I wanted to spend a huge amount of money on expensive shoes and I can afford it, nobody is there to tell me I’m being bad. I’m in control of my money. (although, rereading that, it’s doesn’t sound very mature :dubious: )
And when I realized that people older than me (like my parents age) are real people. For a long time, I had arbitrary classifications that went: peers, grown-ups, kids. Now some “grown-ups” are actually good friends.
Final nail: when I realized that I’m the same age as the parents of some of my clique…
One of my colleagues is somebody I’ve known since we were about nine, and neither of us can call each other ‘Mr Gorillaman’ or ‘Miss Colleague’ in front of the kids while maintaining an entirely straight face.
I also had a bizarre colliding of worlds a couple of weeks back, when a pupil wanted to get in touch about something, and the first thing she did was search for me on Facebook. Receiving a message there which begins ‘Hi sir’ is a bit bizarre.
I thought it was when I drove my wife & firstborn home from the hospital. But parenting, while an adult behavior, is too much fun much of the time to actually drive the point home.
It turned out to be when a bailiff came into the jury selection room and whispered to the judge, who then excused me from jury duty because my wife was rushing our youngest child to the emergency room.
Along the same lines, our kids were born 5 weeks early. Within the first week, I was signing documents, granting permission to perform surgery, as a guardian, of someone I hadn’t known a full week. (Pyloric Stenosis)
When teenage store clerks started calling me “Sir.” Gee, guess I’m an old dude now.
Well, in his dad’s defense, it’s gotta be rough having a human being dangling from your ear all the time.
It’s nice of your grandma to take hers out, though. Dinner and a movie? 
I’ve only felt like an adult a handful of times. The most recent ones were when I filled out my apartment lease on my own, and when I filled out my benefits paperwork at work. Nothing says “adult” like reviewing Accidental Death and Dismemberment forms.
I had a former classmate die unexpectedly our very first day of college. That didn’t make me feel like an adult. It actually made me feel very young.
2 instances:
My Dad passed away 14 years ago, after a sudden illness. I realized that I needed to go back to school and get a degree; because Mom & Dad weren’t able to support me anymore. I crammed 2.5 years into 1.5 years.
Second, putting my Mom into a nursing home. Not filling out the paperwork, researching them, or discussing it with the family. It was loading the luggage the car, and then putting her into the front seat. And driving her from the home she had loved for 25 years.
Eli
It’s been a cumulative thing since getting married. I know it seems ridiculously old-fashioned but getting married seemed a very “grown-up” thing to do, even at age 32. Then my husband had a manic episode and had two hospitalizations in our first year of marriage. Calling 911 in the middle of the night because your husband is having a severe dystonic reaction to medication and has gone completely psychotic, then watching him be put into restraints in the ER is an extremely grown-up experience. I handled everything for months until he was back at 100%.
Buying a house.
Taking in a friend to live with us who was pregnant and had nowhere to go.
Being with her when the baby was born.
Eventually having to lovingly push her out of our nest (I felt like a Toughlove mom).
Supporting my immediate family post-Hurricane-Katrina, and knowing that I’m the evacuation point for the foreseeable future.
Burying my grandmother.
On a less serious note, I feel very grown-up whenever I travel by air. I don’t know why, it just seems vaguely glamorous even though it isn’t at all. 
How about realizing the Playmate of the month was born when you were 18 and could be her Dad.
The day it dawned on me, I was standing in Sears fawning over a washer/dryer set. It was 1997. I was 27 years old. My Granddaddy died in April of that year, and he left each of us 3 grandkids $1000 to do with what we wished. I had been on my own for a few years…I was renting a trailer…money was tight. The washer/dryer set that the landlord supplied was unreliable at best. I decided that the best use of that $1000 would be to buy myself a nice washer/dryer. A very adult decision I thought. But literally standing there in Sears, I realized I was a grown-up.
This is actually the very first thing I noticed when I first became an adult.
The corollary? Realizing ice cream for breakfast every day is not in your long term best-interest and opting for whole grain cereal 99% of the time.
The former revelation is much more exciting than the latter.
I bet you were damned excited for that washer and dryer set, weren’t you? Admit it your old fogey!!! We’re all hopeless.
It’s really weird to see so many of these things come up that I had already done by age 17.
Last biological grandparent died: 2
Liking music from the 70s: 5
Friend with cancer: 7
Investing: 10
Last grandparent died: 10
Preference of prescription bottles: 12
Realizing that it wasn’t cool to like music from the 70s: 13
Classmate died: 14
Taking in a friend with nowhere to go: 17
Spacey.
Maybe not an adult, but not a child anymore.
I looked in the mirror one day, and suddenly realized that I was about to turn 20 and I looked it.
See, I’d always thought that my friends and I, the ones I had known since middle school, never really looked old enough when compared to other people our age. I’d go to inter-school events, or, later, walk around my college campus and think “I know all these people are roughly the same age as me, but they look so much older!”
I still get that same kind of feeling every once in a while looking at kids and realizing that the story I was remembering with a buddy a couple days ago actually happened when we were that small.