Each generation has moments that are indelibly imprinted in its collective memory, moments that are recalled and retold time after time.

My generation knows precisely where we were when John F. Kennedy was assassinated. For our parents, the defining moment of their lives was Dec. 7, 1941 — 75 years ago today.

It was Sunday afternoon on the East Coast and families were finishing their traditional Sunday dinner. Many had turned on the family radio. Up and down the coast, they may have been listening to the live coverage of the Giant and Dodgers baseball game, the National Vespers program or a concert by the New York Philharmonic. In Virginia, many were listening to the Sammy Kaye musical program, Those were pretty much the choices available.

Then, at 2:22 p.m., the Associated Press issued the bulletin that would change the world — and, coincidentally, usher in a new era of nearly instant news. The AP bulletin was the first public report of the attack on Pearl Harbor, and it occurred while the attack was still underway.

Within minutes, news networks had confirmed the initial report to their satisfaction and were breaking into the Sunday afternoon programs to announce what was happening.

I recall my parents saying that they were visiting their neighbors, Grover and Jean Yeoman, and heard the announcement over the Yeoman’s radio.

(A story in today’s Times relates similar remembrances by local residents interviewed this week.)

The shocking announcement that afternoon represented a new era for the then state-of-the-art technology known as radio. In those frightful Sunday afternoon minutes, the radio became the source of immediate news coverage. It was then, and remained for decades, largely a pipeline for news gathered by traditional means for newspapers and wire services, but on that day that radio became the primary “immediate” dispenser of breaking news.

Radio had been around for a good while when Pearl Harbor occurred. President Franklin D. Roosevelt’s “Fireside Chats” were broadcast in the early 1930s. But this was the first major, world-changing event that was revealed to the public via the airwaves. From that cold December afternoon forward, Americans would listen to their radio at least once a day for “breaking” news.

(In our house, during the 1950s, it was WRVA, that powerful Richmond channel with the huge tower on Broad Street.)

The following day, with Americans in a state of shock and fearful of what would come, Roosevelt delivered one of his most powerful speeches. In asking Congress for a declaration of war, Roosevelt delivered one of the memorable line:

“Yesterday, December 7th, 1941 — a date which will live in infamy…”

And, indeed, it has. Americans have never forgotten — and will forget, at their peril — the attack on Pearl Harbor.