It’s been 18 years since a cloudless day in September turned into one of horror in New York City, Somerset County, Pa., and Washington, D.C., and was met by heroism.

Eighteen years is the age of an average high school senior, meaning an entire generation has experienced Sept. 11, 2001, only through historical footage.

Eighteen years is the blink of an eye in the scheme of things, but it feels like a long time. While it’s unlikely that few who were alive at the time have forgotten that day, most people have confined 9/11 to history.

But the families of the 2,996 people who lost their lives — at the World Trade Center, the Pentagon or in a Pennsylvania field where United 93 crashed — have not.

Every year, people gather for ceremonies, services, motorcades and other events to commemorate the lives lost — from the victims of circumstance to first responders who rushed into life threatening situations and either died trying to save others or have suffered from complications in the years that followed.

The crowds are smaller at these events as the years pass, but the families and friends of 9/11 victims annually turn out to revisit the pain they felt on that horrific day.

We owe it to them not to forget.

This year in Butler County, residents are doing their part.

On Tuesday, the Mars-Pine-Richland Area JROTC took over the annual 9/11 flag memorial at Mars High School.

Seneca Valley School District will spend the day Wednesday educating students — none of whom were alive on 9/11 — on the events of that day.

In Evans City, students will be asked to complete three good deeds for people as part of a 9/11 challenge founded in 2002.

This is a great way to build upon the legacy of service inspired by the events of that day.

During an interview some years ago, architect Michael Arad told this editorial writer he was inspired by the way people came together after 9/11, and he used that inspiration to design the memorial at Ground Zero.

“It reflected on our values and a society in which people come together,” he said.

Sept. 11, 2001, will forever be remembered as one of the worst days in our nation’s history, and for many the wounds caused by the day’s events will never heal.

But its legacy can be more than merely the lives that were lost.

It should be a day in which people can be inspired by the brave deeds of those who helped others. It can be a day to not just look back, but also give back.