As a kid, two dates associated with U.S. military history were fairly well known and certainly noted, annually: D-Day, June 6, 1944, when the Allies landed in France to open a second front against the Third Reich, and Pearl Harbor Day, December 7, 1941.

And it was the latter that was the bigger event, come anniversaries — Japan’s surprise attack on the U.S. military facilities near Honolulu.

It resonated on several levels.

America before Pearl Harbor was a very different place than the America after. Before it was an inward-looking country not aware of its own strength and not all that keen to project that power. After? All that changed.

The notion of splendid isolation, a U.S. set off from the rest of the world by two oceans, came to an end, too, as the bombs started falling. Before that morning in Hawaii, lots of Americans believed it was possible to stay out of major international affairs. It was wishful thinking.

Pearl Harbor led directly to the U.S. gearing up for the war effort with the kind of overwhelming energy perhaps never before seen. A nation with an enormous production capacity and resources, both human and material, turned its attention to training soldiers and equipping them. And creating the first nuclear weapon.

The effort also ended the Great Depression. An economic crisis which began in 1929 was still hanging around more than a decade later, but Pearl Harbor changed that, too. Everyone had a job, if they wanted one, within a few months, and the U.S. economy kept blasting right through the rest of the century. At the end of World War II, the U.S. alone accounted for half of the economic activity in the world. A first in world history.

But now … all that seems to be less relevant by the year.

September 11 is a big part of it. Most Americans were alive when the Twin Towers collapsed, in 2001; very few were alive when the Japanese turned to the attack on Battleship Row, 71 years ago, now.

Also, the survivors of the December 7 have nearly vanished. A New York Times story a year ago noted how time has taken so many of those who were in Hawaii that day — to the point that the survivors group has disbanded.

Let’s concede it. Seventy-one years is a long time ago. Not even I remember that. And the meme has changed, too. Pearl Harbor led to a half century of U.S. dominance in global affairs and 20 years as the world’s only superpower. It’s not quite the same now, with the U.S. economy staggering and China and other nations emerging.

For the latter half of the 20th century, December 7 did not go by without stories about that day, and the survivors. I worked at newspapers who always, always did a Pearl Harbor story. Now, those stories are becoming rare. The most recent surprise turning point in U.S. history was a terror attack 60 years later.

Eventually we stop talking about history when it starts to become ancient history. The 1927 Yankees. The Great Depression. Pearl Harbor. Important, sure, but not as important as they were, and not as relevant in our modern lives.”Remember the Maine!” That meant something a century ago; now it hardly does.

We won’t forget Pearl Harbor. But we already are not remembering it the way we did.