docs: public static PeriodType years() {
          PeriodType type = cYears;
          if (type == null) {
              type = new PeriodType(
                  "Years",
                  new DurationFieldType[] { DurationFieldType.years() },
                  new int[] { 0, -1, -1, -1, -1, -1, -1, -1, }
              );
              cYears = type;
          }
          return type;
      }