How do I know this? Well, to start, my definition of "nap time" has completely changed.
PREVIOUS NAP TIME DEFINITON: Getting into bed mid-afternoon with Dennis next to me (don't let him fool you...he is a nap-lover just like I am!).
CURRENT NAP TIME DEFINITION: Taking advantage of any free (and quiet) minute that I have. And, apparently Echo and Connor prefer to use me a a pillow.
Here is the other way that I know:
It's no secret that I am, well, uh...pretty anal... and so it shouldn't surprise you that I keep a log of when Connor eats and when he goes pee and/or poop. Dennis was changing his diaper (Connor's diaper, not to be confused with Dennis' diaper) and I asked him what presents he left for us so that I could update the log appropriately (no pun intended). It was obvious that he had not pooped so Dennis decided to find out if he wet his diaper instead. The scientific method that Dennis used was really the only one that makes sense: he stuck his fingers in the front part of the diaper.
I laughed at him. Not because he used this method but because I've done the same thing. Several times. Hey, it's important to make sure that the log is accurate. And you can always wash your hands.