This function takes two arguments. The first argument is a time value, the second is an integer value. The function increments the month by the second argument and returns the time value for the same day, hour and minute but some months later or sooner in case the second argument is negative.
If the resulting value is on a day that does not exist on the result month then the day part of the result is decreased. For example:
print FormatTime("MONTH DAY, YEAR",AddMonth(TimeValue(2000,03,31),1))
April 30, 2000