Wouldn't this piece of sample code from the included lib-custom.php solve your problem?
Text Formatted Code
// Sample link #2: Link to the Personal Calendar - only visible for
// logged-in users
if (!empty ($_USER['uid']) && ($_USER['uid'] > 1)) {
$myentries[] = array ('url' => $_CONF['site_url']
. '/calendar/index.php?mode=personal',
'label' => 'My Calendar');
}