drupal modify node post on date time

template.php file:

function phptemplate_node_submitted($node) {
return t('!username on @day @datetime',
array(
'!username' => theme('username', $node),
// Here you need little php date function knowledge.
'@day' => format_date($comment->timestamp,'custom','l'),
'@datetime' => format_date($comment->timestamp,'custom','m/d/y'),
));
}