Perfectly normal.
The Wall is still a new album to me. Scuzz played part of it on his 8-track, like, just the other day. It was far out!
Thanks for all the replies but most are related to things that remind you that you are getting old. That is, they fall under the second bullet in the OP “The day you realize you are getting old”.
What I had in mind were milestones in and of themselves.
For example, realizing that you are getting old means “Oh shit, I may not have time to fullfill that lifelong dream of mine”. Realizing that your parents are old means, for example, “Damn, I don’t have that much time left with them”.
So, in addition to things that remind you of getting old, what other milestones are there? Slypork had some examples, like
• First time you realized that your parents had sex for fun. (EWWW)
• First time your kid comes to you all starry-eyed about some boy/girl.
The day you realize that if you’d married at the age your parents did, you’d probably have grandkids by now. O.o
For me, my 25th birthday was the only one that stood out in any way. All I could think of was ‘A quarter of a century!!!’ and for some reason that just seemed…like a milestone, somehow.
The day you realize that you have surpassed your parent(s) in some manner.
I’ll add another: The day you recognize you’re asking advice from your parents, not because you need it, but because it makes them feel good.
I also recall watching my dad ‘grow up’, and can pinpoint just when he stopped treating us ‘kids’ as kids and started mellowing out enough for us to be friends with him.
They day when you stop caring. When you realize you’re gonna die and you better stop whining about things you don’t have and start enjoying what time you have left, by making use of what you do have
Also when you’ve lived longer without your folks then with them. For instance, my father died when I was 11 and mum died when I was 16 and I recall when I turned 33 thinking, “Wow I’ve now lived longer without my folks than with them.”
Loosing pets 1:
Erin (our Irish setter) and I were the same age; we were brother and sister. We were 14 or so when she had to be put to sleep. No way you can escape the wrenching aging affect of that kind of loss.
Loosing pets 2:
The day you lost your first adulthood pet. I got Kitty Garcia in my early twenties. She lived her whole life in the blink of an eye and two or three stages of mine.
Man, holy shit I didn’t expect this to be hard to type. Such a long time to be gone; such a short time to be there.
Loosing pets 3:
Someday in the future I’m not going to get a pet. Someday I’m going to have to make the conscious choice not to take on another animal because it will likely outlive me. Hope that day is a ways off.
Heh, I’ll add another, specifically for those who are parents themselves: the day your parents can say “now you know” about your own childhood transgressions, and all you can do is agree.
Also, the day your parents become really useful to you once more, as grandparents (sadly followed by the day you have to take care of them).
The day you have to go to the bookstore to sell your childhood D&D manuals for bus money to get to job interviews.
When you fill out the legal paperwork because your parent isn’t conscious to consent to be intubated or what have you and suddenly feel more adult than you ever ever wanted to.
The year you go to bed at 10 PM on New Years eve and don’t feel pathetic about it.
When you realize that during your adult lifetime, hairy pubes on women were in fashion, out of fashion, and back in fashion again.
This reminded me of a couple more
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The day you have lived longer with your significant other than without her/him (I haven’t reached this yet, but I assume it will be significant)
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For those who have moved from the place of their childhood: the day you realize that you have lived longer in your new place than in the place you grew up in (I have reached this)
O, my yes. On the other hand, when my mother pesters me about grandkids I can now point out that I’m the age my favorite Grandmother was when my elder brother was born.
Realizing there are things you can count in decades. I’ve been working for three decades.
Suddenly finding myself doing the things my dad did when he first started to get old, like moving a book around until it’s far enough away for me to read it. (Of course, *I’m *not old, I just need new glasses).
The first time you engage the services of a lawyer for yourself (for criminal charges, real estate transactions, a divorce, or other). Only adults get lawyers.
Saying things like, “I have a great lawyer I can refer you to.” 
Getting a new job and being older than your supervisor. Getting a job and being older than ALL of your co-workers.
When I was 24 years old, livin’ the bachelor life, and I bought a box of Kleenex instead of running to the bathroom and using toilet paper. That was a milestone as it meant that I was starting to make home. It sounds a bit silly, but there was a small part of me that wanted to have company and they would just happen to notice a box of Kleenex on the side table and it would change their opinion of me to the better.
The day you realize you’re sleeping with a 50 yr old man!
My own birthdays, just came and went. My own age never wigged me out, 20, 25, 30, 35 - all came and went, no biggie. Then, one day, my husband turned 50 yrs old. I hadn’t thought of it much. We’re neither the type, really. But once it dawned on me, I couldn’t get over it. All year, I kept telling people, “I can’t believe I’m sleeping with a fifty year old man!” Incredulous, I was. Took me a whole year to get used to the idea.
The day where you start talking to kids about things that happened about ten years ago…only to realize that they weren’t even ALIVE then.
The day when you start not caring about your birthday.
The first time you’re offered a Senior Citizen discount. (Often well before you’re actually qualified to get one.)
The day you realize that you don’t have to do what your mother says anymore, because by the time she was the age you are now, she was divorced for the second time with two kids.
(And that goes double for Mom’s relationship advice, as you might imagine.)
How about, when you start a story by saying, “A few years ago…”
And then you realize, in mid-sentence, it wasn’t “a few” years ago, it was 10 or 20 years ago.
Would finding one’s dad’s porn stash (when you weren’t looking for it!) count? Because I did, when we were cleaning out his apartment after he died (very young, very sudden, quite sad really) and I was seventeen and I found The Stash. At which point I realized that my Daddy had…masturbated. Pass the brain bleach! In retrospect, it was pretty damned funny, what with some intervening time and all.
This was half my life ago, this May. Weird. I know I wasn’t quite an adult, but I wasn’t all that far from it either. I think this should count.
Ewwwww.