Unfortunately, mermaid brings its own moment.js which is bundled inside, and we do not have access to their copy of moment to change the locale.
The docs on their site seems to just be a copy from mermaid’s official site that states how to change the locale, but since Mermaid is bundling their copy of moment without exposing publicly, we don’t have access to it.
Might need to file an issue and hope the mermaid team gets around to expose that, or allow using an external mement.js which we’re using anyway.