The Is month equals operator is used to select dates with a month value that exactly matches the MM component of the date that is entered in the condition input field. All other date components are ignored.
Setting the Date condition of a Birth date field to Is month equals, and entering 12/12/1978 as the input field value, selects all those contacts whose birth month matches that value. In this instance, all contacts born in December are selected.
The Is month equals operator applies to date data types.
See Input field types for more about each input field.