Echo JS 0.11.0

I've always thought the UX for the date picker from the MS Ajax Toolkit is about as good and intuitive as it gets, it looks like the bootstrap-datepicker implements this... unfortunately, it also requires jquery+bootstrap, and if you aren't using bootstrap to begin with, it's too big to bring in just for this. Range pickers are also easy to get wrong.

In any case, for the most part, just use input type=date and rely on the native interface for picking a date. You aren't adding a bunch of extra overhead, and it should be the expected experience.