change your code to:
<?php
$ano = $registracion->DisplayInfo("ID");
echo("ano = ".$ano."<br />");
$quiru= date('Y-m-d', strtotime('+ $ano Year')); echo $quiru;
?>
and post back what that writes to the screen
i think:
$quiru= date('Y-m-d', strtotime('+ $ano Year')); echo $quiru;
should be:
$quiru= date('Y-m-d', strtotime('+'.$ano.' Year')); echo $quiru;