I see in the news today that Avengers Infinity War release date has been moved to one week earlier. I am curious usually how long before release date of movies (blockbuster movies to be more specific) the production is complete, is it matter of days or one month or maybe longer? For example in software engineering we hope to finish the development and testing before the release date to account for unexpected problems or issues. Is there the same concept in movie production?
Joss Whedon shot Avengers post-credit scene on the day of premiere. Ridley Scott didn't finished his "Blade Runner" till 25 years after it's premiere in 1982.
There's a difference between studio desired release date and creator(s) feel and need to finish the movie.
Studios release date is usually calculated based on time needed to shot the movie, montage, reshooting some scenes, adding FX, preparing marketing materials, preparing copies, sending movies to different countries if they are distributed there, securing actors time to promote the movie AND THEN figuring out if the movie won't collide with any other premiere so first weekend won't be a flop.
And then all those calculations goes into the gutter because the new guy hired to do just montage decide he need to put CGI clean upper lip on guys moustache.
In the Avengers case the push to one week earlier may by dictated by the premiere of Deadpool and Solo movies. So to "wear" the movie in cinemas and earn more money before next thing will arrive and take a portion of audience.