The two major events like that, probably in most of our lifetimes, were the Challenger and 9/11/01.
For me it took months before the enormity of the second really sunk in. My mind didn't want to seem to wrap around that many people dying. The first tears I shed, were actually when I saw Congress on the steps of the Capital, singing "God Bless America."
And I was 6 when Challenger exploded, I grasped it, but I didn't.
It takes me time before BIG STUFF sinks in.
Pearl Harbor, JFK's assassination, the Challenger, and 9/11/01.
40s, 60s, 80s and the noughts. (My mind desperately wants to make a pattern out of that.)
Those are the big ones, the "events that defined a generation," and "moments when everyone remembers where they were."
But what are the non-whole world moments?
What are the big moments in your life that changed the way you viewed the world, that make up a big part of who you are?