For a moment I was skeptical, but after looking at the codebase, it's almost exactly what I would do: wrap Intl.DateTimeFormat with a few small functions that basically just help enforce that the expected type matches the provided type, with just a tiny touch of additional coercion to make the native API a little less surprising.

I've been trying to reduce my dependencies in favor of "vanilla" APIs, but it's hard to argue with the minimalist way this is organized around the Date object.

Kudos to the creators!