Ooh, so glad you posted 'cuz maybe you have an answer to one of the great questions I’ve pondered throughout my life:
Olde-timey phone numbers like “Butterfield 8” – does this mean you dial a "B’ then an “8” to connect to an operator, who in turn patches your call through to Mrs. Astor Von Vanderbilt?
Exchange prefixes were generally two letters, so “BRoadway 27218” would have the ‘b’ and ‘r’ dialed before the number. It never made a lot of sense to me, as it was all numbers.
What makes me feel old is when I go to a museum or an antique store and there’s all this shit that I grew up with.
Realizing how many people I knew in my life are now likely dead.
Thinking about how many people are alive who regard 9/11 as a historical thing. We lived through it.
Yep, I was in the 9/11 Museum and was struck by how many kids there weren’t alive when it happened. The Today Show footage many of us watched live that morning is now an exhibit in the museum.
Today I checked out the new Pokemon Go app. Not only did I have no idea how to play, I realized I didn’t care and deleted it.
The kids born on the day that I was old enough to drink are now old enough to drink.
Yesterday, I saw a car commercial with Frank Zappa’s Willie The Pimp as background music. Not the vocals, of course, but still, all US broadcasting had a blanket ban on anything Zappa for a very long time.
Early telephone exchanges, with mechanical switches and even manual switching, had significant physical plant and were decentralized and localized, and named. “Broadway exchange” had a real place, and it was more convenient and easier to name them than number them. That became less necessary over time, but by then, “Broadway 27218” had long been your number and the habit stuck.
What just made me feel old was a high school class came to one of my university lectures and the teacher came over and said, “I took a course with you.”
Ringo Starr’s first grandchild turns 31 this year.
The President of the United States is younger than me.
All of the Ramones (the original ones, anyway) are dead.
I vaguely remember the Latin Mass.
Some years ago, a young lawyer at the firm where I was working told me that his mother went to grade school with me.
For me it is knowing that all the people who were considered young sex symbols when I was a kid are now in their 50s.
Just thought of another one. I’m an adjunct professor at a local university. Most of my students were born after I started college.
When I was in college, my friends and I were amused and confused when one of our middle aged professors did an impression of the Cajun Man character from SNL. That must be how my students feel when I drop memes into my lecture decks.
Dear god, what have I become?
The thing that makes me feel old . . . is actually being old.
The first worldly even I remember was Queen Elizabeth’s Coronation in 1953. My mother sat me down in front of our little Zenith TV with its 12" round b&w screen, and said “Watch this. It’s something you’ll always remember.” I had no idea that, 63 years later, Elizabeth would still be Queen.
And yeah, I was already a freshman in college when JFK was assassinated and the Beatles were on Ed Sullivan.
That one really got me. But there’s also the following, for me.
Bishop of my Episcopal diocese.
My doctor.
My dentist.
My hairdresser
Plus other’s. At least my pet’s vet is a little older than me.
Well the realisation that for most teenager today the 1990’s the decade which I grew up in was one that happened before they were born or they had no memory off.
My Dad went back for his Military Academy reunion recently and he learned that one of the Cadets fathers was born the same year my Dad was commissioned.
Every time I read Click Clack Moo to my elementary students, I have to preface it by explaining what a typewriter is, since it’s central to the story. “It’s like a computer that only runs MS Word and prints as you’re working,” I tell them. Then they go, “Oooooooh!” with a look of dawning comprehension.
One of the standardized language tests I give has a question asking students to explain how to use a pay phone. I’m 28, and those were going out when I was my students’ age. Why they haven’t come out with an updated version of this test, I don’t know. Same with the vocabulary labeling tests that show a picture of a pocket calculator, and all the students say “iPhone.”
I found out about the 9/11 attacks… on the SDMB.
Seeing 3 different doctors in an 8 day span. Yes, the pain in my fingers and hands is arthritis, I shouldn’t wait too long to get a hernia fixed and I should consider knee replacement surgery within the next year. 2 of the 3 gave me free Viagra samples. 
Mirrors
The first major league baseball game I ever attended, I saw two players who were born more than 100 years ago (Enos Slaughter, Emil Verban). I got Slaughter’s autograph after the game, which was played in one hour and 32 minutes, tickets were $1.85. I’ve seen MLB games in eight decades.
I am a few months older now than Carroll O’Connor was when All in the Family first aired. Yes, I am older than Archie Bunker.
By the end of this year I will be older than Patrick Stewart was when Star Trek: The Next Generation first aired.