An anachronism is an error that relates to time. Usually events, objects, or people are misplaced in time with regards to each other. If you used a quill to write something or wore a top hat, that would be anachronistic. The science fiction genre is particularly susceptible to anachronism, especially as the "future" time that a work was set in approaches, and all is not as the author proposed.
. You can find more information here: http://en.wikipedia.org/wiki/Anachronism
