code: public DatePicker setDateFormat(String dateFormat) {
          SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
          sdf.setLenient(false);
  
          return setDateFormat(sdf);
      }
docs: Sets the date format for this element.
  It also changes the date format for the date validator, if present.
  @param dateFormat Date format
  @return This element