Twenty-five years ago this Friday, the world changed.

If you are old enough to remember Sept. 11, 2001, you probably remember exactly where you were. You remember the room, the television, the people around you and the strange feeling of trying to understand something that did not yet seem real.

I was a senior in high school. The school year had barely begun. I remember walking into school after an early morning seminary council meeting and seeing televisions turned on in some of the classrooms. Back then, most of the classrooms had those little televisions mounted high in a corner. Teachers had turned on the news, and images from New York filled the screens.

I sat down in a classroom and watched for a few minutes, trying to piece together what was happening. Going from one class to the next, it was the same that day. We watched television. My band room did not have a TV, so our teacher wheeled one in. We didn’t play much music that day.

I think it was my AP writing class where we actually stopped and talked about what was happening and what it might mean. It felt like something from a Hollywood movie, except it wasn’t a movie. People were dying. There was evil in the world, and suddenly it had come to us.

I was 17 years old, just a couple of months away from turning 18. I remember thinking that soon I would be old enough to join the military. I wondered whether I should. I wondered whether we were going to war. The thoughts frightened me. I remember questioning everything and trying to make sense of how something like this could happen. Looking back, those thoughts remind me how suddenly the world had become real.

We had watched the 2000 presidential election and followed the Florida recounts. But politics still seemed distant. Sept. 11 may have been the first time I really understood that events happening thousands of miles away could change my future and the lives of everyone around me.

Now, somehow, 25 years have passed.

I was born in 1983. In that year, 1958 was 25 years ago — the same distance separating us today from Sept. 11. As a kid, 1958 would have seemed like ancient history. Sept. 11 certainly doesn’t.

I can still see those little televisions in the corners of the classrooms. I can still picture the television being wheeled into the band room. Twenty-five years sounds like a long time until you measure it against something that changed your life. Then it can feel like yesterday.

For millions of Americans, Sept. 11 is more than a date in a history book. It is the last phone call from someone they loved, an empty chair at a family table, a firefighter climbing a stairwell while everyone else was trying to get out or the passengers of Flight 93 realizing what had to be done. It is New York City, the Pentagon and a field in Pennsylvania. It is also the military deployments, families separated, lives lost overseas and first responders who carried the consequences of that day for years afterward.

This year we mark 250 years since the signing of the Declaration of Independence and 25 years since the attacks of 9/11. One anniversary reminds us how our nation began, and the other reminds us how quickly the world can change. Remembering is not about living in the past. We remember so we can learn from it. We remember courage, sacrifice and ordinary people who, in extraordinary circumstances, chose to help someone else. We remember those who answered the call to serve and those who never came home.

So this Friday, ask yourself a simple question: Where were you on Sept. 11, 2001? And after you remember where you were, remember those who never got to see Sept. 12.