http://github.com/jquery/jquery-ui add "js" directory in language directory eg: /langs/fr_FR/js/ move datepicker language file eg: /langs/fr_FR/js/jquery.ui.datepicker-fr.js and rename the file eg: /langs/fr_FR/js/jquery.ui.datepicker.js
http://github.com/jquery/jquery-ui add "js" directory in language directory eg: /langs/fr_FR/js/ move datepicker language file eg: /langs/fr_FR/js/jquery.ui.datepicker-fr.js and rename the file eg: /langs/fr_FR/js/jquery.ui.datepicker.js