docs: private static int parseMillis(Input s) {
      if (s.index < s.len && s.getChar() == '.') {
        int startIndex = ++s.index;
        int ms = parseInt(s);
        int len = s.index - startIndex;
        for (; len < 3; len++) ms *= 10;
        for (; len > 3; len--) ms /= 10; // truncate because it's easier than rounding.
        return ms;
      }
      return 0;
    }