Sarah Cohen ’18 remembers being sent home from school early on Sept. 11, 2001, and crying with her parents in the family room of her house in Baltimore. She was five at the time.

That same day, Gabriela Viera ’18 — then six years old — had the TV news on in her kitchen in New Jersey while her mother assured her that her father, who worked in Manhattan, was safe.

But hearing stories like Cohen’s and Viera’s is becoming less and less common as a generation of college students graduates and younger ones come to take their place. As the 15th anniversary of 9/11 itself moves into memory, Yale and other colleges nationwide face a situation familiar to history: Many college students do not remember the day at all, and those who do can paint the scene only in the broadest of strokes.

Soon, there will be an entire crop of Yale undergraduates who not only have no recollection of the Sept. 11 attacks, but were born after they took place.

“This is the dividing line between history and memory, and the history beyond memory,” said David Blight, an American history professor at Yale who serves as an advisor to the National 9/11 Memorial and Museum team of curators.

Nine Yale alumni died at Ground Zero: David Berray ’84, David Berry ’80, Bennett Fisher ’66, Elizabeth M. Gregg GRD ’77, Bradley Hoorn ’01, Richard Lee ’91, Charles McCrann LAW ’72, Christopher Murphy ’88 and Stacey Sanders ’98. But it is impossible to estimate exactly how many Yale community members have been affected by the Sept. 11 attacks, how many future community members will have been and in what ways.

Charlie Pasternak ’18 and Ginger Li ’18 only recall that school ended early that day for both of them. Li’s mother, who worked in New York City, came home late because all lines of transportation between Manhattan and her home in New Jersey had been cut. Other than that, the day is completely lost for them.

Dean of Undergraduate Admissions Jeremiah Quinlan was a junior at Yale getting ready for class in the morning when he heard on his radio that the Twin Towers had been hit. Both of his parents were working in New York at the time, and it took hours for him to get in touch with them.

Quinlan described the day as a long period of shock and grief among the student body. At night, there was a candlelight vigil on Cross Campus that the whole school attended, he said.

Jack Kyono ’20 said he remembers Sept. 11 because it was his first day of preschool. He was let out early, but had no idea what was happening, he said.

Still, students who do not remember the actual event will still have at least heard about their having grown up in a post-9/11 world, Blight said.

“We are often not very clear about being part of a self-conscious generation, and the very idea of a generation is not always well defined,” he said. “But we are all shaped by large external events, huge political turning points, the pivotal moments that shape our thinking, conscious or not always conscious.”

When he was young, Kyono used to go swimming at a spot in his hometown of Montclair, New Jersey, that had a fantastic view of the Manhattan skyline. He remembered vividly the outline of the Twin Towers, two rectangles towering above the other skyscrapers.

One day in the summer 2002, Kyono went back to the pool and noticed that something was missing, that the Twin Towers were gone. The skyline had changed. That is how he remembers 9/11, and how future generations of Yale students will remember it, too: The world is different, but the difference for them is not as clear.