I'm in the US and I've never heard of 2015-04-03 being interpreted as March 4. I just see the standard interpretation as logical, since it's coarse (year) to fine (day).
Well, on the other hand, 'customary' US order is MM-DD-YYYY based on how we normally (verbally) say dates.
Honestly, its perfectly ok for an application to use whatever standard date format - as long as its clear and consistent within the application - at least in the context of North America, where everything is a mishmash of whatever standards you can imagine.
Hell, .Net datetimes specifically allow you to output in whatever format the current OS default is set to (or you can choose your own).
No, like July 4th. Or July 5th. Or October 31st. The 4th of July is a notable exception, and the GP's point of how we "normally (verbally) say dates" stands.
