The default BoxPress date format for your posts is
"MM d, y" which produces September 6, 2018 as the exported date string. The format string is embedded inside a larger bit of code, which I have placed in the previous sentence as well. The full bit of export code is
^value(date("today").format("MM d, y"))^.
Here are the ingredients you can use to export an alternatively formatted date:
MONTH MM: full name of month ▶︎ April M: three-char name of month ▶︎ Apr m: number of month ▶︎ 4 M0: two-digit number of month (zero-padded) ▶︎ 04 YEAR y: full 4 digit year ▶︎ 1999 Y: 2 digit year ▶︎ 99 DAY d: day of month ▶︎ 9 D: two-digit day of month (zero-padded) ▶︎ 09 W: full name of weekday ▶︎ Tuesday w: three-char name of weekday ▶︎ Tue TIME H: hour on 12-hour clock (use with p) ▶︎ 8 h: hour on 24-hour clock (zero-padded) ▶︎ 08 p: the AM or PM of the hour ▶︎ AM mm: minute (zero-padded) ▶︎ 01
For an informal 9/6/18 : use
For a neater, zero-padded 09/06/18 : use
For a more formal and sortable 2018.09.06 : use
For a diary-esque Thursday, September 6 : use
"W, MM d"
The definitive description of date formats can be found in Mark Anderson’s aTbRef.