II sure convert this string in the Index.english.php file (and rename it to index.vietnamese.php then set this language for default)
Quote$txt['days'] = array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday');
$txt['days_short'] = array('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
// Months must start with 1 => 'January'. (or translated, of course.)
$txt['months'] = array(1 => 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');
$txt['months_titles'] = array(1 => 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');
$txt['months_short'] = array(1 => 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
Example: January = ThÃÆ'Ã,¡ng giÃÆ'Ã,ªng
February = ThÃÆ'Ã,¡ng hai ....
But why this string (day, month) still not show corect (still show english string) in my forum ?