* @return true if this is equal to the other period
   */
  @Override
  public boolean equals(Object obj) {

    if (this == obj) {
      return true;
    }
    if (obj instanceof Period) {
      Period other = (Period) obj;
      return this.years == other.years && this.months == other.months && this.days == other.days
          && this.nanos == other.nanos;
    }
    return false;
  }