code: public long getInstantMillis(Object object, Chronology chrono) {
          String str = (String) object;
          DateTimeFormatter p = ISODateTimeFormat.dateTimeParser();
          return p.withChronology(chrono).parseMillis(str);
      }
docs: Gets the millis, which is the ISO parsed string value.
  
  @param object  the String to convert, must not be null
  @param chrono  the chronology to use, non-null result of getChronology
  @return the millisecond value
  @throws IllegalArgumentException if the value if invalid