ADD_MONTHS(t,a) is a date function that determines a date in the future or a date in the past.

Value t: When used in a function, the expression t (date_or_timestamp_expression) must supply a date, a time stamp, or an alphanumeric value that matches the current date or time stamp format.

Value a: The expression a (expression) supplies a numeric value that represents a number of months. Any decimal places in a are truncated if necessary.

If t is the last day of the month or if the resulting month has fewer days than the day component of t then the result is the last day of the resulting month. Otherwise, the result has the same day component as t.