This happens to me quite often. I know I have seen the film because it's on my list of films I have seen, but I don't remember a second of it. And it's not because I have a bad memory...
Ditto to that, only I'd push the date back to 1985. One example: I went to ROMEO IS BLEEDING when it first came out, 1993, probably it's opening day, and I haven't seen it since and can't recall any of it. There are many other examples during a period of my life, 1985 thru 2000, when I used to go to a movie a week. Now, I go maybe once every two months. I've gotten older, but movies have gotten more mediocre.
I have a vague memory of the Star Trek reboot remembering only that I found it an insult to my intelligence. What happened in the film I could not say.
I can't remember The Dark Knight Rises either except that it was a miserably depressing movie. A filmmaker who doesn't believe in the very concept of the thing should leave it alone and move on to something else.
Other films I can't remember:
The League of Extraordinary Gentlemen The Phantom Menace Attack of the Clones Revenge of the Sith Iron Man Iron Man 2 Iron Man 3 Superman Returns The Avengers Cowboys vs Aliens The Green Hornet The Fantastic Four The Hunger Games -- the first one Spiderman 1 Spiderman 2 Spiderman 3 The Amazing Spiderman The Amazing Spiderman 2 Superman: Man of Steele -- actually, I remember thinking this must have been made by a serial killer or a sociopath it's so sadistic.