Seven years is a fraught span of time. Jacob worked seven years for Leah, and then another seven years for Rebecca. Joseph's Egypt had seven fat years followed by seven years of famine. Grade school legend says it takes seven years to digest swallowed gum, and breaking a mirror gives you seven years of bad luck. Marilyn Monroe tempted Tom Ewell in The Seven Year Itch, and it used to take seven years to recover from bankruptcy (though I think it may now be ten -- anyone know?). Michael Apted chose seven years as the appropriate interval for his documentaries about a group of British schoolchildren as they grew up.
I remember hearing somewhere that all the cells in the human body replace themselves over seven years, so that every seven years each of us is a new person. (I don't understand how that phenomenon interacts with the aging process, but never mind.)
So today is the seventh anniversary of the attacks on the World Trade Center and the Pentagon. It seems almost unbelievable that it's been seven years already, but I also have a hard time remembering the world as it was on September 10, 2001, before everything changed. I used to be able to drive my car down Pennsylvania Avenue, right past the White House; as recently as when I was in college, people could buy tickets right on the airplane, the way you can on trains.
I don't know what I think about the idea of a national holiday on September 11. Maybe it's not a great idea. Veterans' Day and Memorial Day used to mean more than sales and a free day off, and I'd hate to see the same thing happen to September 11. What would we call it, anyway?