protected function setYearParameter($key, $value)
    {
        // normalize year to four digits
        if (null === $value || '' === $value) {
            $value = null;
        } else {
            $value = (int) gmdate('Y', gmmktime(0, 0, 0, 1, 1, (int) $value));
        }

        return $this->setParameter($key, $value);
    }