Hi. There is an option named " Date & time format" in the module edit page. You can see the acceptable values at
php.net/manual/en/function.strftime.php . If you want a common format for both languages then you can use this option. If not set this to :
and then create a template override for the module and use the Joomla! language variable:
<?php echo JHtml::_('date', $feed->itemDate, JText::_('DATE_FORMAT_LC1')); ?>
Let me know if you need more help.