I've heard this said about quite a lot of media, including "I Am the Walrus" (the Beatles' song), the original Spider-Man comics by Stan Lee and Steve Ditko, and the Watchmen graphic novel. All stories that meant a great deal to me at the time I discovered it and which I still love to this day. All of which first came out before I was born.
This makes me skeptical of the entire concept of stories becoming "dated".
I do think there are some media (like this delightful Simon and Garfunkel song) that contain so many references to contemporary events that a person simply can’t understand them without being familiar with the context.
But then, is understanding the same as enjoyment? After all, people love the Bible and apply to their own lives, while large parts of it are only understandable if you know about the context in which is written. I love the book of Ecclesiastes in ways that have nothing to do with understanding the world in which it was written. While I disagree with the vast majority of biblical interpretations, but I don’t think people are mistaken or wrong when they say they enjoy it and connect to it. Despite the fact that most of these people don't know much about the context in which is was written.
The Bible is one of the most "dated" books in the world, and yet look at its reputation in Christian-heavy cultures.
I sometimes wonder if claiming that something is "dated" is a way of holding onto the myth that "classic" media was better than modern media. I've always assumed the reason people think, for example, that 1930s and 1940s movies were better than modern movies, is because people usually see only the good movies from that era, and not the crap. And when they do encounter the crap, they can just say that it's "dated".
I recall someone once referring to the Dead End Kids as "dated". The Dead End Kids were a group of actors/characters who played/were a group of young hoodlum characters. They appeared in theater and film from the 1930s to the 1950s. I've only seen them in one film (a gangster flick called Angels With Dirty Faces), but that's enough for me to tell you this: The Dead End Kids are not dated. The Dead End Kids suck. They sucked in 1938, and they suck now.
One day people will describe Twilight as dated. And still, there will be people who read it and enjoy it and connect to it. But this I believe: Twilight will never be "dated". Twilight will suck, because Twilight already sucks.