The default BoxPress date format for your posts is "MM d, y" which produces 3月 12, 2017 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

Examples:

For an informal 3/12/17 : use "m/d/Y"

For a neater, zero-padded 03/12/17 : use "M0/D/Y"

For a more formal and sortable 2017.03.12 : use "y.M0.D"

For a diary-esque 日曜日, 3月 12 : use "W, MM d"

The definitive description of date formats can be found in Mark Anderson’s aTbRef.