Change the "Submitted by" date type?
It's hard-coded into template_preprocess_node() so to override it you'll need to implement your own preprocess function, either in a theme or custom module:

function MYTHEME_preprocess_node(&amp;$vars) {
  if (variable_get('node_submitted_' . $vars['node']-&gt;type, TRUE)) {
    $date = format_date($vars['node']-&gt;created, 'date_type');
    $vars['submitted'] = t('Submitted by !username on !datetime', array('!username' =&gt; $vars['name'], '!datetime' =&gt; $date));
  }
}