code: public DateTimeFormatter withChronology(Chronology chrono) {
          if (iChrono == chrono) {
              return this;
          }
          return new DateTimeFormatter(iPrinter, iParser, iLocale,
                  iOffsetParsed, chrono, iZone, iPivotYear, iDefaultYear);
      }
docs: Returns a new formatter that will use the specified chronology in
  preference to that of the printed object, or ISO on a parse.
  <p>
  When printing, this chronology will be used in preference to the chronology
  from the datetime that would otherwise be used.
  <p>
  When parsing, this chronology will be set on the parsed datetime.
  <p>
  A null chronology means no-override.
  If both an override chronology and an override zone are set, the
  override zone will take precedence over the zone in the chronology.
  
  @param chrono  the chronology to use as an override
  @return the new formatter