282     protected $byMonth;  variable in Sabre\\VObject\\Recur\\RRuleIterator
336         if (!empty($this->byMonth)) {
363             ($this->byMonth && !in_array($currentMonth, $recurrenceMonths))
494         if (empty($this->byMonth)) {
634                 } while (!in_array($currentMonth, $this->byMonth));
660             } while (!in_array($currentMonth, $this->byMonth));
771                     $this->byMonth = (array) $value;
772                     foreach ($this->byMonth as $byMonth) {
773                         if (!is_numeric($byMonth) || (int) $byMonth < 1 || (int) $byMonth > 12) {
963         foreach ($this->byMonth as $byMonth) {
964             $recurrenceMonths[] = $byMonth;