Thanks Pascal, but it still returns the same date <b> 'Jeudi 1 Janvier à 01h00' </b> (french format) for <b>all</b> my files. As if the actual published date was ignored ...
Once "in" the override of your datatype, you no longer have <i>directly</i> access to the $node var. Instead, you should use something like <b>{$attribute.object.published}</b> to get access to your object published date.