A new widget that shows a calendar based on existing post types.
<ul>
<li>Select any available post type to show</li>
<li>Filter by any custom taxonomy term tied to the selected post type</li>
<li>List a maximum of 10 items below calendar</li>
<li>Set a prefix for every listed item</li>
<li>Filters and hooks</li>
</ul>

WordPress Calendar For Custom Post Types

Because the builtin calendar doesn't have such an option.

hashtechy

Easy Custom Post Type UI offers a simple to use interface for creating and maintaining taxonomies and custom post types for your website.
This plugin is written using only native functions, included in WordPress core, so it does not in any way reduce the performance of your website and will not cause any compatibility problems. Easy Custom Post Type UI is completely free, it will save you time and it is compatible with almost all themes and plugins out there.

Easy Custom Post Type UI

Easy Custom Post Type UI offers a simple-to-use interface for creating and maintaining taxonomies and custom post types for your website.

WordPress Calendar For Custom Post Types vs Easy Custom Post Type UI