I remember watching The Hurt Locker (starring Jeremy Renner), the movie is meant to depict the Iraq War in 2004 but for some reason there’s a scene where an iPod Touch (releases in 2007), XBOX 360 (releases in 2005) and Gears of War (releases in 2006) present in the barracks even though these did not exist yet. Another anachronism from this movie is when a American soldier spots an Iraqi recording him ready on uploading the footage via YouTube (the website didn’t exist yet until 2005 when the story is set in 2004).
Compare that to most medieval movies with an orchestral soundtrack. Orchestras are full of instruments that only achieved their current form in the last couple hundred years.