For anyone fortunate enough to get an Elder Scrolls Online key a while back when they gave away thousands upon thousands of them here,

ESO July Login Rewards

include the Clockwork City DLC on July 2nd.
Login that day to get it.
If I recall, their day resets at 2 AM EDT, so anytime after that you should be good to claim it.
(I can never tell if stuff like this should go in Game Talk or Deals and Freebies, but last time I posted in Game Talk and I don't think it found it's audience there.)