Yes you are right, the same is also by me.
What I mean is that today, day, week and year will also be translatet. I don’t want to have an mix.
First of all it is important that you use more then one language in your project. You can check this in studio pro by going to the top bar → languages → language settings. Here you can add new languages to the project.
When a user creates an account he can set his preferred language, or you can change this at any time later in the account_overview screen. If you implement the Mendix calendar widget now it will automatically adept to the language the user has set as preferred language.
Hope this answers your question!