The Bedford Glossary of Critical and Literary Terms - Ross Murfin 2018
Anachronism: Something outside of its proper historical time period. When this “error” occurs, an author places an event, person, or thing during a time when it could not have existed.
EXAMPLES: The clock that strikes in William Shakespeare’s Julius Caesar (1598), for no such clocks existed in the Rome of Caesar’s time. The film A Knight’s Tale (2001), described by critic David Ansen in Newsweek as “wildly anachronistic,” includes a scene in which the crowd at a medieval jousting tournament not only sings along to “We Will Rock You” (1977), a heavy metal song by Queen, but also does “the wave.”