291     protected $byMonth;  variable in Sabre\\VObject\\Recur\\RRuleIterator
349         if (!empty($this->byMonth)) {
379             ($this->byMonth && !in_array($currentMonth, $recurrenceMonths))
514         if (empty($this->byMonth)) {
660                 } while (!in_array($currentMonth, $this->byMonth));
689             } while (!in_array($currentMonth, $this->byMonth));
807                     $this->byMonth = (array)$value;
808                     foreach ($this->byMonth as $byMonth) {
809                         if (!is_numeric($byMonth) || (int)$byMonth < 1 || (int)$byMonth > 12) {
1007         foreach ($this->byMonth as $byMonth) {
1008             $recurrenceMonths[] = $byMonth;