byMonthDay

Specifies which day of the month the event should occur on (1-31). Used with MONTHLY or YEARLY frequency to schedule events on specific date within a month.

Examples: [15] for events on the 15th of each month, [-1] for events on the last day of month.

Note: It does not accept multiple values in the same list. If a specified day doesn't exist in a particular month (e.g., day 31 in February), the event will be skipped for that month. This field cannot be used simultaneously with ByWeekdayOccurrence as they represent different scheduling approaches (specific dates vs. relative weekday positions).