I've been asking Cortana to "set up a dentist appointment for July 27th". Sure enough, she echoes back the text perfectly, but invariably, she sets it up for July 1st, not the 27th? What's going on?
I think I found the problem. The "the" between "July" and "27th" was throwing Cortana off. When I ask for "July 27" or "July 27th", instead of "July the 27th" Cortana gets it right. I didn't think it was overly idiomatic to include "the" (e.g., "July the 4th".) Seems like something Cortana should understand.