Don’t hack the language file, bad practice...
Rather use Ditto dateFormat and dateSource parameter as instructed in Ditto’s doc.
Example :
[tt]&dateSource=`pub_date` &dateFormat=`%d %m %Y`[/tt]
(check
strftime for valid date format)
This will work for document lists...
On the document page use PHx filter : [tt][*pub_date:date=`%d %m %Y`*][/tt]
If you need localized date then don’t forget to add setLocale, best way is to create a little snippet and place it before the doctype (top of templates) :
<?php
setlocale (LC_ALL, ’fr_FR.UTF-8’);
?>
Adjust the locale to your need of course