The MonthOfYearMask property returns a combination of flags indicating which months of the year are to be included in a recurrence pattern.
RecurringAppointment, RecurringEvent, and RecurringTask objects
Long
Read/write
The first twelve bits of the MonthOfYearMask property represent the months of the year. Bit 0 is January; bit 11 is December. Bits 12 through 31 are ignored. For example, to indicate January, March, and April with this property, set bits 0, 2, and 3.
RecurringAppointments
RecurringEvents
RecurringTasks
RecurringType