public function daysInMonth(): int
    {
        try {
            return $this->calendar->daysInMonth($this->year, $this->month);
        } catch (InvalidArgumentException $ex) {
            // calendar.php calls this with "DD MMM" dates, for which we cannot calculate
            // the length of a month. Should we validate this before calling this function?
            return 0;
        }
    }