Using the management API you can get the first message age by calling queueControl.getFirstMessageAge(), but in the case of the activemq.notifications address you get a milliseconds value which corresponds to more than 50 years. This is because the message timestamp is not initialized here so it defaults to zero. So we actually have: now - 0 = 2020 - 1970 = 50 years.

We already set the _AMQ_NotifTimestamp property that could be used to compute message age so I was wondering if we could also initialize the message's timestamp to the same value and fix this weird value, but I don't know if there is any side effect.