docs: public static String formatTimeDelta(long time, CharSequence sep) {
      final StringBuilder sb = new StringBuilder();
      final Formatter fmt = new Formatter(sb);
  
      for(int i = TIME_UNIT_SIZES.length - 1; i >= 0; --i) {
        // We do not include ms if we are in the order of minutes.
        if(i == 0 && sb.length() > 4) {
          continue;
        }
        // Separator
        if(sb.length() > 0) {
          sb.append(sep);
        }
        final long acValue = time / TIME_UNIT_SIZES[i];
        time = time % TIME_UNIT_SIZES[i];
        if(!(acValue == 0 && sb.length() == 0)) {
          fmt.format("%0" + TIME_UNIT_DIGITS[i] + "d%s", Long.valueOf(acValue), TIME_UNIT_NAMES[i]);
        }
      }
      fmt.close();
      return sb.toString();
    }