What changed with movie tickets?

In early November 2018, I bought tickets to see Bohemian Rhapsody. My mom was turning 70, and she wanted her whole family to go. The show I bought tickets for was on December 30th. So, to reiterate, a little more than a year ago, in early November 2018, I bought tickets to see a movie that I was going to go to see several weeks later. I can not do that anymore. Is it just me? Can you but tickets three or four weeks out on Fandango, or on your local theater's ticketing site? If it is just me, what am I doing wrong? If it isn't just me, why did the vast majority of movie theaters recently ALL decide at the SAME time that you have to wait until Tuesday before you can buy tickets for a Friday movie?