code: public static Period between(final Period type, YearMonth startInclusive, YearMonth endExclusive) {
          int dayOfMonth = 1;
          return Period.between(
                  DateTimeExtensions.leftShift(startInclusive, dayOfMonth),
                  DateTimeExtensions.leftShift(endExclusive, dayOfMonth))
                  .withDays(0);
      }
docs: Obtains a Period consisting of the number of years and months between two {@link java.time.YearMonth} instances.
  The days of the Period will be zero.
  The result of this method can be a negative period if the end is before the start.
  
  @param type           placeholder variable used by Groovy categories; ignored for default static methods
  @param startInclusive the start {@link java.time.YearMonth}, inclusive, not null
  @param endExclusive   the end {@link java.time.YearMonth}, exclusive, not null
  @return a Period between the year/months
  @see java.time.Period#between(LocalDate, LocalDate)