protected function evalFlagGrouping($config, $flag)
    {
        if (($flag < 0) || ($flag > 12)) {
            return;
        }

        if ($flag <= 4) {
            $config->setGroupingMode(GroupAndSortingInformationInterface::GROUP_CHAR);
        } elseif ($flag <= 6) {
            $config->setGroupingMode(GroupAndSortingInformationInterface::GROUP_DAY);
        } elseif ($flag <= 8) {
            $config->setGroupingMode(GroupAndSortingInformationInterface::GROUP_MONTH);
        } elseif ($flag <= 10) {
            $config->setGroupingMode(GroupAndSortingInformationInterface::GROUP_YEAR);
        } else {
            $config->setGroupingMode(GroupAndSortingInformationInterface::GROUP_NONE);
        }
    }