I think the better/easiest way is using the simpler bidirectional component template Code snippet: create Components without any frontend tooling (no React, Babel, Webpack, etc) and building your calendar input there.
The HTML method does not send back data to Python as it only displays a static render (Doc Components API). To be honest it could be feasible to hack your way through it through JS hacks that basically revolve on rebuilding the full bidirectional function from the template, which is a bit sad 
Have a nice day,
Fanilo 