private function upgradeProperty(PropertyMetadata $property, NodeInterface $node, $locale, $up)
    {
        $name = sprintf('i18n:%s-%s', $locale, $property->getName());
        if (!$node->hasProperty($name)) {
            return;
        }

        $value = $node->getPropertyValue($name);

        if ($up) {
            $value = $this->upgradeDate($value);
        } else {
            $value = $this->downgradeDate($value);
        }

        $node->setProperty($name, $value);
    }