code: public DateTimeFormatter withZone(DateTimeZone zone) {
          if (iZone == zone) {
              return this;
          }
          return new DateTimeFormatter(iPrinter, iParser, iLocale,
                  false, iChrono, zone, iPivotYear, iDefaultYear);
      }
docs: Returns a new formatter that will use the specified zone in preference
  to the zone of the printed object, or default zone on a parse.
  <p>
  When printing, this zone will be used in preference to the zone
  from the datetime that would otherwise be used.
  <p>
  When parsing, this zone will be set on the parsed datetime.
  <p>
  A null zone means of 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 zone  the zone to use as an override
  @return the new formatter