Thank you Portia for being a sounding board. DD is a different child these days and she no longer watches science programs or reads science books. She seems to be getting into dinosaurs a little bit but her interest seems superficial. I was surprised that she even brought up this topic out of nowhere. Since she is thinking these things on her own at an intuitive level rather than through exposure to external sources, I wasn't sure how much I should get involved in her thought process. She is rather indifferent about learning units of time although she gets very distracted by timers.

She hasn't talked about time again since then so I'm going to talk a wait-and-see approach.