code: public final Timestamp addYear(int amount)
      {
          if (amount == 0) return this;
  
          Calendar cal = calendarValue();
          cal.add(Calendar.YEAR, amount);
          return new Timestamp(cal, _precision, _fraction, _offset);
      }
docs: Returns a timestamp relative to this one by the given number of years.
  The day field may be adjusted to account for leap days.  For example,
  adding one year to {@code 2012-02-29} results in {@code 2013-02-28}.
  
  @param amount a number of years.