The maintenance is now complete:
The maintenance is complete, and the #ESOTU console megaservers are now back online and available. Thank you for your patience!
— Elder Scrolls Online (@TESOnline) June 29, 2015
At 7:30am PT/10:30am ET, maintenance to the log-in and account systems for The Elder Scrolls Online began on PlayStation 4 and Xbox One.
Expected to last for five hours (until about 12:30pm PT/3:30pm ET), Zenimax explains that currently logged-in players won’t be affected by the maintenance:
On Monday, June 29th, we will be performing maintenance on the console login and account systems starting at 10:30AM EDT/4:30PM CEST. During this time, you will be unable to log into the game or your game account but the megaservers will remain up. Those who are already in the game when the maintenance begins will be able to continue playing. We expect this maintenance to last approximately five hours—we will keep you updated if that changes.
Similarly, the PlayStation Network will be undergoing maintenance later tonight/early tomorrow. We’ll send out a reminder when the PSN is undergoing maintenance.
If you’ve yet to download update 1.04 for The Elder Scrolls Online, which launched on June 24, keep in mind that it’s a 15.9GB download.
[Source: Elder Scrolls Online Forums]
The Elder Scrolls Online Down for Maintenance On PS4 and Xbox One, Logged in Players Can Keep Playing