docs: public static String encodeDateTime(DateTimeField field)
      {
  		Date date = ((DateTimeField)field).getDateTime();
  		if (date == null)
  			return null;
      	if (field instanceof TimeField)
      		return timeFormat.format(date);
      	else if (field instanceof DateField)
      		return dateFormat.format(date);
      	else // if (field instanceof DateTimeField)
      		return dateTimeFormat.format(date);
      }