code: public static Period between(final Period type, Year startInclusive, Year endExclusive) {
          MonthDay now = MonthDay.of(Month.JANUARY, 1);
          return Period.between(
                  DateTimeExtensions.leftShift(startInclusive, now),
                  DateTimeExtensions.leftShift(endExclusive, now))
                  .withDays(0)
                  .withMonths(0);
      }
docs: Obtains a Period consisting of the number of years between two {@link java.time.Year} instances.
  The months and 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.Year}, inclusive, not null
  @param endExclusive   the end {@link java.time.Year}, exclusive, not null
  @return a Period between the years
  @see java.time.Period#between(LocalDate, LocalDate)