code: protected int handleGetLimit(int field, int limitType) {
          if (field == ERA) {
              if (limitType == MINIMUM || limitType == GREATEST_MINIMUM) {
                  return BEFORE_MINGUO;
              } else {
                  return MINGUO;
              }
          }
          return super.handleGetLimit(field, limitType);
      }
docs: Override GregorianCalendar.  There is only one Taiwan ERA.  We
  should really handle YEAR, YEAR_WOY, and EXTENDED_YEAR here too to
  implement the 1..5000000 range, but it's not critical.