protected function get_day_names(renderer_base $output) {
        $weekdays = $this->related['type']->get_weekdays();
        $daysinweek = count($weekdays);

        $daynames = [];
        for ($i = 0; $i < $daysinweek; $i++) {
            // Bump the currentdayno and ensure it loops.
            $dayno = ($i + $this->firstdayofweek + $daysinweek) % $daysinweek;
            $dayname = new day_name_exporter($dayno, $weekdays[$dayno]);
            $daynames[] = $dayname->export($output);
        }

        return $daynames;
    }