code: public void setGWTFormat(final String format) {
          this.format = toBootstrapDateFormat(format);
  
          // Get the old value
          final Date oldValue = getValue();
  
          // Make the new DateTimeFormat
          this.dateTimeFormat = DateTimeFormat.getFormat(format);
  
          if (oldValue != null) {
              setValue(oldValue);
          }
      }
docs: Sets format of the date using GWT notation
  
  @param format date time format in GWT notation