OK, first off, I am two years older than you, not five or six.
Secondly, I figured it out. You go by gener's of humor. For example, a friend that is four years older than me hates Adam Sandler & Will Ferrell. He really enjoys Animal House. Meanwhile, I don't get Animal House, & quite enjoy Adam Sandler & Will Ferrell. A friend 4 years younger than myself doesn't like Sandler or Will Ferrell. So I judge generations by humor of movies & actors.