A login queue is not an outage
On a busy launch day the realm closes logins once it is full and puts new arrivals in a queue. That queue is the server working as intended, not failing. Closing the game and reopening it drops you to the back of the queue, so the instinct to restart is the wrong one in this case.
Telling maintenance apart from a connection fault
A scheduled maintenance window affects everyone on the realm at once, and the announcement for it is published through the publisher's official channels for your region rather than in game. If other players on the same realm are online and playing while you cannot reach the server, the problem is on your side — check the client version first, then your network.
If nobody on the realm can connect, and a maintenance notice is up, it is the server. The distinction matters because the two have opposite fixes: one you wait out, the other you troubleshoot.
Tracking the schedule yourself
Maintenance windows move the events around them. When a realm comes back up, the event cycle usually resumes on the server clock rather than shifting to accommodate the downtime, which means a rift opening can land very shortly after the servers return or seem to skip a slot.
The rift timer on this site reads the schedule from the server clock rather than from a list of absolute times, so it stays correct across a maintenance restart as long as the cycle itself is unchanged. If a notice changes the cycle, the page is updated and the review date moves forward.