Ah, anachronisms! A powerful rhetorical tool when used effectively, a fascinating rhetorical indicator species when used by accident. Here’s what Wikipedia has to say on the subject:
Comedy fiction set in the past may use anachronism for humorous effect. One of the first major films to use anachronism was Buster Keaton‘s The Three Ages, which included the invention of Stone Age baseball and modern traffic problems in classical Rome. Comedic anachronism can be used to make serious points about both historical and modern society, such as drawing parallels to political or social conventions.
Language anachronisms in novels and films are quite common, both intentional and unintentional. Intentional anachronisms inform the audience more readily about a film set in the past. Language and pronunciation change so fast that most modern people (even many scholars) would have difficulty understanding a film with dialogue in 17th-century English; thus, we willingly accept characters speaking an updated language.
According to the article, Sir Walter Scott made a similar – although more general – argument in support of anachronism:
It is only since the close of the 18th century that this kind of deviation from historical reality has jarred on a general audience. Sir Walter Scott justified the use of anachronism in historical literature: “It is necessary, for exciting interest of any kind, that the subject assumed should be, as it were, translated into the manners as well as the language of the age we live in.”
So, adapting historical works carries on in ancient tradition! Although I think there’s a lot to be said for varying your rhetorical diet – personally, I enjoy a mix of modern adaptations and renderings that strive for historical accuracy. Each brings different things to the table.