When you're five, you know your age down to the month. Even in your twenties you know how old you are. I'm twenty-three, you say, or maybe twenty-seven. But then in your thirties something strange starts to happen. It's a mere hiccup at first, an instant of hesitation. How old are you? Oh, I'm--you start confidently, but then you stop. You were going to say thirty-three, but you're not. You're thirty-five. And then you're bothered, because you wonder if this is the beginning of the end. It is, of course, but it's decades before you admit it.