public function dateformat(array $submitted, array $options)
    {
        $options += array(
            'field' => null,
            'label' => null
        );

        $value = gplcart_array_get($submitted, $options['field']);

        if (strtotime($value) === false) {
            return $this->setErrorInvalid($options['field'], $options['label']);
        }

        return true;
    }