You need to use a plugin or file edit to add some php to take that date and put it into a useable format:
PHP Code:
$userinfo['date'] = vbdate($this->registry->options['dateformat'],$userinfo['joindate']);
$userinfo['time'] = vbdate($this->registry->options['timeformat'], $userinfo['joindate']);
$userdateline = $userinfo['date'] .' '. $userinfo['time'];
Something like that. You may be able to just use $vbulletin->options instead of $this->registry->options . It depends on where the plugin is hooked in.