There have been 2 days like that in my lifetime. Turning point days, milestone days. Days where something so significant happened you know you will always remember where you were when you first heard the news. One was Friday November 22, 1963. I was in my 6th grade elementary school class. The other was Tuesday, September 11, 2001.
This is what my parents say too.
I remember our principal did the announcements, which was very odd, and we definitely noticed the teachers acting strange, but it wasn't till before lunch they brought us in and told us what happened and turned on the tvs. A couple girls cried and most of us just sat there watching it, one of the edgy kids laughed and everyone got pissed at him.
My brother and his best friend, who was basically a brother to me, came to pick me up, but at that point I wasn't really surprised. My dad was an administrator in a school system and my mom ran the booster club and some other shit, so I figured they'd be busy.
Anyways we got home and they headed back out, I went up and turned on cartoon network hahaha, I was so happy something was normal that day...
Those people are idiots. I suppose it could be argued that the direct consequences of the attack were small, but there's no doubt it was the single most world changing event since the fall of the USSR. I mean, and if this offends you I both understand and apologize, in my opinion the terrorists won.
19 years later we're still caught in wars as a result of the attacks. The rise of extreme idpol and partisanship is a result of 9/11, as well as the hesitation of our European allies to help us with Iran. bin Laden's goal was to weaken American influence and harm the American people. He succeeded with both of those goals.
September 11th, 2001 will always be remembered, one way or another, at least as long as the current world civilization endures, and that's, in my opinion, the definition of a very consequential event.
There's only one other day I remember with anything like the clarity of 9/11, and that was the space shuttle Columbia disaster. I didn't even keep up with space stuff, but seeing a marvel of American ingenuity, engineering, and production capabilities go down in flames due to some foam was a very humbling thing for me to see.