code: public void setDate(
              final int year,
              final int monthOfYear,
              final int dayOfMonth) {
          Chronology c = getChronology();
          long instantMidnight = c.getDateTimeMillis(year, monthOfYear, dayOfMonth, 0);
          setDate(instantMidnight);
      }
docs: Set the date from fields.
  The time part of this object will be unaffected.
  
  @param year  the year
  @param monthOfYear  the month of the year
  @param dayOfMonth  the day of the month
  @throws IllegalArgumentException if the value is invalid