pickadate.js

pickadate.js is the jQuery date picker that doesn't require Bootstrap. It's 8kb gzipped, supports keyboard nav, multiple languages, date ranges, and time pickers. 7.7k stars. The original maintainer (Amsul) is no longer maintaining it but the project is on the maintainers-wanted list. The biggest issue: it's tied to jQuery, which limits its appeal in the modern React/Vue/Angular world. But if you're shipping a Rails app or a WordPress plugin, pickadate is still one of the cleanest date pickers available. A rescue would either: (a) maintain the jQuery version for legacy use, or (b) fork into a vanilla JS version (no jQuery) which is a much bigger lift.