code: public static String timestampToString(Timestamp ts) {
          return TIMESTAMP_FORMAT.get().format(ts)
                  + String.format(".%09d-00:00", ts.getNanos());
      }
docs: Return a String suitable for use as an edn {@code #inst}, given
  a {@link Timestamp}.
  @param ts must not be null.
  @return an RFC3339 compatible string.