Anachronism

An anachronism, from the Greek ana ("against") and khronos ("time"), is "a chronological inconsistency in some arrangement, especially a juxtaposition of people, events, objects, language terms and customs from different time periods." "The most common type of anachronism is an object misplaced in time," but the list runs from verbal expressions and technologies to customs. Severity sorts them too: a parachronism "appears in a time period in which it is not normally found," while a prochronism is "an impossible anachronism which occurs when an object or idea has not yet been invented." "Anachronisms abound in the works of Raphael and Shakespeare," and not all are slips: Sir Walter Scott defended a historical subject "as it were, translated into the manners as well as the language of the age we live in."

The writer's discipline is research plus proofreading, because "unintentional anachronisms may occur when a writer, artist, or performer is unaware of differences" between eras, the failure how to write historical fiction exists to prevent. Even the future dates: "science fiction writers risk anachronism as their works age." And in a serial the error is published, not drafted, so a gadget or idiom fifty chapters early cannot be quietly deleted, only retconned, the line drawn in retcon versus continuity error.