3906 days is a long amount of time. It's the number of days that have passed since September 11, 2001. Looking down at the bottom right corner of my computer screen, it says "9:13 PM, 9/11/11". Only a P and a 1 would have to change for this to be the time in which our country was completely and entirely devestated, outside in the city and in our hearts.
There's nothing I can say about the events of 9/11 that have not already been said or that will have any more of an impact than the images in our minds. But pictures can say a lot more about what happened than words, so here are some from TIME magazine. They will really bring out a new side of it that most people can't remember.