protected function getPublishedFormat(array $config)
    {
        if (isset($config['publishedFormat'])) {
            if (!is_string($config['publishedFormat'])) {
                throw new \DomainException(
                    'publishedFormat must reference a string',
                    self::ERR_INVALID_PUBLISHEDFORMAT
                );
            }
            return $config['publishedFormat'];
        }
        return 'n/j/y g:i A';
    }