code: @Deprecated
      public static void appendEpoch(StringBuilder buf, long timeMillis) {
          buf.append(dateTimeFormatter.format(Instant.ofEpochMilli(timeMillis)))
             .append('(').append(timeMillis).append(')');
      }
docs: Formats the given epoch time in milliseconds to typical human-readable format
  "yyyy-MM-dd'T'HH_mm:ss.SSSX" and appends it to the specified {@link StringBuilder}.
  
  @deprecated Use {@link #appendEpochMillis(StringBuilder, long)}.