Growing up quickly

I am writing this today because time is flying and I don't want to forget when this happened. Zach has not yet reached the 100 day milestone in kindergarten, but I just keep feeling as if his academic achievements do not reflect that. At all. He's counting change, telling time, doing simple multiplication, reading most anything, writing complete sentences, and carrying on conversations about Martin Luther King, Jr., faith matters, government and all things science and space. At least one thing hasn't changed in the last four years - his love of science. He reads his homework assignments to himself, reads text messages as I type them, and even likes to read the label on the milk jug while he eats cereal. It seems as if he went from being a little boy that we could easily talk in code around, to a miniature grown-up who hears and understands most everything overnight. Why has this time-flying thing caught me by surprise?