Certain movies simply stand the test of time. As the years pass, it becomes clear which films are designated as classics, to be passed down for generations to come. After a while, though, the timeline becomes a little hazy. With so many movies released each year, it can be easy to lose track of time. Next thing you know, you wake up and your favorite movie is nearing its 25th or 50th anniversary.

Here are ten movies that have remained so popular over the decades you haven’t realized how old they truly are.

Gallery — Movies You Won't Believe Are Rated G: