We'll create fresh WordPress site with WP Better Calendar installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This Plugin enables you to choose any post type (that is public) to show the posts based on a beautiful calendar that will be parsed on the widget location. It is compatible with almost all themes, it is tested with. But in case you found any theme where the plugin is not working correctly. You can add an issue on Github Repository.