code: public long getInstantMillis(Object object, Chronology chrono) {
          Date date = (Date) object;
          return date.getTime();
      }
docs: Gets the millis, which is the Date millis value.
  
  @param object  the Date to convert, must not be null
  @param chrono  the non-null result of getChronology
  @return the millisecond value
  @throws NullPointerException if the object is null
  @throws ClassCastException if the object is an invalid type