Today I am grateful for my gracious and cheerful friend who smiled and nodded and claimed it was no problem at all. She would be glad to return tomorrow and the misunderstanding about the date was probably hers when in fact, I realized later, the blame rested squarely on my shoulders. Thank you, friend, for being you.
Note to self: Anytime you are talking/writing about a date be sure to include the actual day (Monday, Tuesday etc.) as well as the number. That way when you say come over at 10 on Thursday, July 17th your invitee will be able to clue in that you have no idea what you are talking about.