Site is using the en_us language pack, which should display short dates as MM/DD/YY but they are displaying in the Euro/Aus format of DD/MM/YY. One location with the incorrect format is the Starting From Date in the Enrol pop-up (Course Settings > Users > Enrolled Users > Enroll Users > expand Enrollment Options).

The en_us language pack is missing the 'strftimedatefullshort' string in langconfig.php. Since the string isn't found, it's defaulting to the same string in the en language pack.

I'm not sure how to make a patch for a language pack but en_us just needs this line:

$string['strftimedatefullshort'] = '%m/%d/%y';

I copied it from en and simply flipped the %d and %m.