Format Follies

I've been puzzling over an invoice I got in an email, with an invoice date of 3/6/2017 and a due date of 10/6/2017.

Why, in June, would a company send me an invoice dated March, that isn't owed until October?

Figured it out today, when I got an overdue notice. It's obvious if you don't live in the U.S., I suppose. Those are June dates - it's that foreign date format!

I was taken in, I fear
by the dreaded day/month/year!