
Earlier this month we learned that Joaquin Phoenix was in talks to star in The Joker origin movie, and things seem to be moving rather quickly.
According to a document posted by reporter Jeff Sneider, production on The Joker is expected to begin this May. That could mean Warner Bros. is planning to release the movie next summer. Right now 2019 has Shazam in the spring (April 5), Wonder Woman 2 in the fall (November 1), and a Joker movie in the summer would fill in that gap quite nicely.
The document below is dated “December 14, 2017” so things could have changed, but if all goes according to this plan the movie should be starting production in just a few months.

The Joker will take place outside of the DC Extended Universe where Jared Leto plays the Joker. It will be part of a new brand of DC movies from Warner Bros.
SOURCE: Jeff Sneider