What makes a novel "a classic"?

For all of my life, every time I heard the word "classic" I thought it was some sort of genre or a way of classifying books. But over time, I learned that classics are considered any novel that is timeless; a novel that has human nature characteristics that will be current in any era of time. (I know that was pretty good--and no I didn't go to the dictionary). But, classics are not only books that have been written 50-100 years ago, like Shakespeare and Bronte, but they can also be modern classics, like Catch 22 (although I've never had the chance to read it), that will also be timeless, but the only change would be the time in which it took place.

What do you think?

Always happy to hear your thoughts. 

B.