static public function getDateFormatter()
    {
        if (is_null(self::$service)) {
            $ext = common_ext_ExtensionsManager::singleton()->getExtensionById('tao');
            $service = $ext->getConfig(self::CONFIG_KEY);
            self::$service = $service instanceof DateFormatterInterface
                ? $service
                : new EuropeanFormatter();
        }

        return self::$service;
    }