docs: public static Years yearsBetween(ReadablePartial start, ReadablePartial end) {
          if (start instanceof LocalDate && end instanceof LocalDate)   {
              Chronology chrono = DateTimeUtils.getChronology(start.getChronology());
              int years = chrono.years().getDifference(
                      ((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis());
              return Years.years(years);
          }
          int amount = BaseSingleFieldPeriod.between(start, end, ZERO);
          return Years.years(amount);
      }