public function byMonths(int $months): Date
    {
        return $this->monthTo($this->originalDate->month() + $months);
    }
public function byMonths(int $months): Date
    {
        return $this->monthTo($this->originalDate->month() + $months);
    }
public function byMonths ( int $ months ) : Date { return $ this -> monthTo ( $ this -> originalDate -> month ( ) + $ months ) ; }
changes date by given amount of months

@api
@param   int  $months
@return  \stubbles\date\Date
changes date by given amount of months