How can I change the language of this calendar?

Question

JavaScript

How to change the localization of the calendar ? As I understand it, there is no documentation for this calendar, it is written in pure js.
Perhaps there are some methods from under the hood that can change the language?

Answer 1

Add locale and fix header class:
I didn’t figure out how to make Monday the first day, because obviously it was done through the back (they would do it normally, the first day would automatically change with the locale).