Hi Sokevin!
If there is no prospect of your date having a day number >=29:
=DATE(YEAR(A1),MONTH(A1)+5,DAY(A1)
But if the base date could have a day number >=29, you may prefer that
the date returned is the last day of the month if that day number
doesn't exist 5 months from the 1st of the base date month. In that
case use:
=DATE(YEAR(A1),MONTH(A1)+5,MIN(DAY($A$1),DAY(DATE(YEAR(A1),MONTH(A1)+6,0))))
This formula is adapted to allow copying down or across to generate a
series of dates 5 months apart.