With the completion of issue 2551390 - Replace text input/calendar popup with
native date input; committed nothing dealing with the calendar is an issue anymore.

With issue 2551353 - Add roundup-classhelper for 2.4.0 release; in the codebase
most of the classhelper use cases are complete. This does leave:

  non-javascript use cases open

  use cases for classhelper where REST is not available an templating is required
       to provide something for the user.