code: public static Months between(CalendarMonth m1, CalendarMonth m2) {
  
          PlainDate d1 = m1.atDayOfMonth(1);
          PlainDate d2 = m2.atDayOfMonth(1);
          return Months.between(d1, d2);
  
      }
docs: /*[deutsch]
  <p>Bestimmt die Monatsdifferenz zwischen den angegebenen Kalendermonaten. </p>
  
  @param   m1  first calendar month
  @param   m2  second calendar month
  @return  month difference