Language
The language of the app and of these docs, and how it differs from the language of a resume, which decides how its own dates are written.
There are three different things that are called language here, and keeping them apart avoids most confusion.
The interface
The language of menus, dialogs, messages and the tours. It is English for now, and more languages are planned. When there is more than one, Settings gains a section to choose one, which applies at once and is remembered on the device, and each language is named in itself, so someone who has landed in one they cannot read can still find their own.
The language of a resume
Each resume has its own language, set in the Style tab under Language, in Document. It formats month names, writes the end of an ongoing role, and sets the language of the exported document. It does not translate anything you wrote, and it is separate from the interface: a resume in French can be written in an app set to English. See Design tokens.
The names of sections the format recognises, such as Experience, are recognised in English and in Indonesian whichever the document's language is. See The shape of the file.
These docs
The documentation is in English, at /en/docs, and opening /docs with no
language sends you there. A language added to the app is added here too, at the
same addresses with its own code in place of en.
What is not translated
The names of the export formats, the three typefaces, and the prompts for an assistant stay in English on purpose, in every language. A resume's own text is yours and is never translated.