When did that happen?

Somehow, I've managed to go gray. Not terribly gray, not yet, but I let my hair grow out (sheer laziness), and today when I went in to have the highlights updated, the hair on top that they pulled through the little cap to highlight was mostly gray. Hey! Of course, now it's mostly blond. In good news, though, it's just the top of my head. From about halfway down it's still dark brown.