Не по-русски как-то получается.
Зато по буржуйски

Заменяем
administrator\components\com_content\models\article.xml
<param name="created" type="calendar" default="" label="Created Date" description="DETAILCREATED" />
<param name="publish_up" type="calendar" default="" label="Start Publishing" description="DETAILSTART" />
<param name="publish_down" type="calendar" default="" label="Finish Publishing" description="DETAILFINISH" />
на
<param name="created" type="calendar" default="" label="Created Date" description="DETAILCREATED" format="%d.%m.%Y" />
<param name="publish_up" type="calendar" default="" label="Start Publishing" description="DETAILSTART" format="%d.%m.%Y" />
<param name="publish_down" type="calendar" default="" label="Finish Publishing" description="DETAILFINISH" format="%d.%m.%Y" />
Дальше
administrator\components\com_content\controller.php
$form->set('created', JHTML::_('date', $row->created, '%Y-%m-%d %H:%M:%S'));
$form->set('publish_up', JHTML::_('date', $row->publish_up, '%Y-%m-%d %H:%M:%S'));
if (JHTML::_('date', $row->publish_down, '%Y') <= 1969 || $row->publish_down == $db->getNullDate()) {
$form->set('publish_down', JText::_('Never'));
} else {
$form->set('publish_down', JHTML::_('date', $row->publish_down, '%Y-%m-%d %H:%M:%S'));
}
На
$form->set('created', JHTML::_('date', $row->created, '%d.%m.%Y %H:%M:%S'));
$form->set('publish_up', JHTML::_('date', $row->publish_up, '%d.%m.%Y %H:%M:%S'));
if (JHTML::_('date', $row->publish_down, '%Y') <= 1969 || $row->publish_down == $db->getNullDate()) {
$form->set('publish_down', JText::_('Never'));
} else {
$form->set('publish_down', JHTML::_('date', $row->publish_down, '%d.%m.%Y %H:%M:%S'));
}