Method getInvoiceDate

public static function getInvoiceDate($orderId, $date = false, $formatOutput = '')
{
    $date = !$date ? self::getOrderDate($orderId) : $date;
    $dateTime = new DateTime($date);
    if ($formatOutput != '') {
        return HTMLHelper::date($dateTime->format('Y-m-d h:m:s'), $formatOutput);
    } else {
        return $dateTime->format('Y-m-d h:m:s');
    }
}