code: protected static void noteMessage (SpeakObject sender, Name username, UserMessage msg)
      {
          // fill in the message's time stamp if necessary
          if (msg.timestamp == 0L) {
              msg.timestamp = System.currentTimeMillis();
          }
  
          // Log.info("Noted that " + username + " heard " + msg + ".");
  
          // notify any message observers
          _messageOp.init(sender, username, msg);
          _messageObs.apply(_messageOp);
      }
docs: Notes that the specified user was privy to the specified message. If {@link
  ChatMessage#timestamp} is not already filled in, it will be.