Here is an amusing conversation that I had with Katie today.
Me: Katie, what day of the week is it?
Me: And what day of the week will it be in seven days?
Me: And what about in nine days?
Katie: Um.., Tuesday.
Me: Tuesday? What about in eight days?
Me: Does Monday come after Friday?
Katie: No, but Saturday and Sunday are the weekend, so they don’t count!
Somehow they counted for the first seven days, but not for the last two :-). It didn’t take me long to make Katie realize the flaw in her reasoning, and then we had some good laughs about it.