Windows Key --->Settings (gear looking icon)
Tab twice until the top Left hand icon is highlighted (SYSTEM). Arrow Right 1 Time, Arror Down 1 time. That is time and language, select it.
Tab Once, so the left hand column has focus, Down arrow 1 time, aqnd hit enter. this is language.
Here is the screenshot of the languages. Add, or change the defualt langauge here. This is where you would add languages if you wished to author word documents in another language, BTW!