docs: private Long string2long(String text, DateTimeFormat fmt) {
          
          // null or "" returns null
          if (text == null) return null;
          text = text.trim();
          if (text.length() == 0) return null;
          
          Date date = fmt.parse(text);
          return date != null ? UTCDateBox.date2utc(date) : null;
      }