code: private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
          stream.defaultReadObject();
          this.era = JapaneseEra.from(isoDate);
          int yearOffset = this.era.startDate().getYear() - 1;
          this.yearOfEra = isoDate.getYear() - yearOffset;
      }
docs: Reconstitutes this object from a stream.
  
  @param stream object input stream