Post History
The only way this is permissible (in my view, of course) is if the main character or the narrator is actually a time traveler from the future. It isn't the setting you need to stay faithful to, it...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/36636 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/36636 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
The only way this is permissible (in my view, of course) is if the main character or the narrator is actually a time traveler from the future. It isn't the **setting** you need to stay faithful to, it is the mind of the narrator, which is usually of the same mind as the Main Character. If your main character came from 2020, sure, they might think of the sword as being as black and shiny as a new car, and the narrator typically knows everything the main character knows. (In 1st person for sure, also in 3rd person omni or limited). Other than that, this is likely to be so jarring an editor / publisher will reject the work as too amateurish; they likely will not finish reading the sample. (They get far too many submissions to give anybody the benefit of the doubt; one jarring error and off you go to the reject pile).