It depends on how new the movie is and what day you want to see it. A day or two should suffice.
Now that all of the seats are Premium Plus seitzer generally available even the day of. But if it's a really popular movie I would suggest getting it in advance. I booked seats for movies a month out.
Yes, Kaylene is right, sometimes a movie that's been out a few weeks will be available the same day. New releases of big movies sell out really fast
Thanks! Your answer is awaiting moderation.