If you are using (or creating) a LANGUAGE PACK, then the date formatting is governed in the main language.php file. (where "language" is the language of the specific language pack you are using.)

For example:

@setlocale(LC_TIME, 'en_UK.ISO_8859-1'); (would show dates in UK ENGLISH)
@setlocale(LC_TIME, 'fr_FR.ISO_8859-1'); (would show dates in FRENCH)