Thanks to the creative power and genuine effort of thousands of authors and playwrights throughout the ages, classic literature has come to mean many things.
In speaking about classics, perhaps the first things that comes to mind is English literature of the 16th, 17th and 18th centuries, it could also mean French literature from the second half of the 17th century, or the golden age of Rome, or Greek literature in its entirety.
Past chronological editions, classic literature has come to mean a work of timely excellence; a book that stood the test of time, be it in argument, language, prose or story.
More commonly, a classic is a story that has transcended its time to become a pop fairy tale, told to children by older generation as a tale of education and woe. It becomes a story of humanity, for humanity, and by humanity.