If you want change the date format, you need change the english.php file in this path: 

/componnets/com_docman/themes/default/language/english.php

change 

<?php
...
define('_DML_TPL_DATEFORMAT_LONG', '%m/%d/%Y %H:%M');
define('_DML_TPL_DATEFORMAT_SHORT', '%m/%d/%Y');
...
?>
to 
<?php
...
define('_DML_TPL_DATEFORMAT_LONG', '%d/%m/%Y %H:%M');
define('_DML_TPL_DATEFORMAT_SHORT', '%d/%m/%Y');
...
?>

it will be ok now.