As pointed out in another comment, it's under the form elements, not listed as a top-level component as many UI libraries do
https://oat.ink/components/#form
Which actually makes sense: Oat's driving philosophy seems to be to use and enhance native controls as much as possible, and the date picker is already a native type on the input element.
But there's no enhancement here. That's just the native date picker control with a bit of styling on the textbox portion of it.
Thanks, I missed that when looking through the component list on the top level.