code: public function createService(ServiceLocatorInterface $serviceLocator)
      {
          $helper = new DateFormat();
          $helper->setLocale(Locale::DEFAULT_LOCALE);
          return $helper;
      }
docs: Creates an instance of \Core\View\Helper\Params
  
  - injects the MvcEvent instance
  
  @param ServiceLocatorInterface $serviceLocator
  @return \Core\View\Helper\Params
  @see \Zend\ServiceManager\FactoryInterface::createService()