The DayOfMonth element is an optional child element of the Recurrence element (section 220.127.116.11) that specifies the day of the month on which the meeting recurs. It is defined as an element in the Email namespace.
The value of this element is an integer data type, as specified in [MS-ASDTYPE] section 2.5.
This element is required when the Type element (section 18.104.22.168) is set to a value of 2 (that is, the meeting recurs monthly on the Nth day of the month), or a value of 5 (that is, the meeting recurs yearly on the Nth day of the Nth month each year).
For examples that show how to set meeting recurrence intervals, see section 4.2.