One of our customer integrations uses all of MM-DD-YY, YY-MM-DD and DD-MM-YY for a date input. Took us quite a few man-hours to figure out why our integration layer failed so often.
;-)
That said, HN is sufficiently international that mentioning the date format to avoid confusion is good.
But looking at the Keck open data archive or the time conversion utility NASA hosts I found little evidence they frequently use anything else than standard iso dates.
Silly anecdote: I have family in Scotland. Prior to getting married, we sent "save the date" cards to them. The listed date was "6/3/06" (June 3) and they were sent in February. Of course, first response from an uncle: "Well, you didn't give us much heads-up. Is she 7 months pregnant?"