code: public CalendarMonth plus(Months months) {
  
          if (months.isEmpty()) {
              return this;
          }
  
          long value = this.year * 12L + this.month.getValue() - 1 + months.getAmount();
          int y = MathUtils.safeCast(MathUtils.floorDivide(value, 12));
          Month m = Month.valueOf(MathUtils.floorModulo(value, 12) + 1);
          return CalendarMonth.of(y, m);
  
      }
docs: /*[deutsch]
  <p>Addiert die angegebenen Monate zu diesem Kalendermonat. </p>
  
  @param   months      the count of months to be added
  @return  result of addition