protected function dayNamesAbbreviated(int $day_number): string
    {
        static $translated_day_names;

        if ($translated_day_names === null) {
            $translated_day_names = [
                /* I18N: abbreviation for Monday */
                0 => I18N::translate('Mon'),
                /* I18N: abbreviation for Tuesday */
                1 => I18N::translate('Tue'),
                /* I18N: abbreviation for Wednesday */
                2 => I18N::translate('Wed'),
                /* I18N: abbreviation for Thursday */
                3 => I18N::translate('Thu'),
                /* I18N: abbreviation for Friday */
                4 => I18N::translate('Fri'),
                /* I18N: abbreviation for Saturday */
                5 => I18N::translate('Sat'),
                /* I18N: abbreviation for Sunday */
                6 => I18N::translate('Sun'),
            ];
        }

        return $translated_day_names[$day_number];
    }