Changes the permalink for a custom post type

custom-post-type-rewrite.php

<?php
/**
 * Plugin Name: Custom URIs for Podlove Publisher
 * Description: Changes the URIs for the episode custom post type of the Podlove Publisher
 * Author: Dennis Morhardt
 * Version: 1.0
 * Author URI: http://www.dennismorhardt.de/
 */

/**
 * Removes the rewrite flag from the podlove custom post type
 * 
 * @since 1.0.0
 */
add_filter('podlove_post_type_args', function($args) {
	$args['rewrite'] = false;
	return $args;
});

/**
 * Changes the permalink for a custom post type
 *
 * @since 1.0.0
 * @uses $wp_post_types
 * @uses $wp_rewrite
 */
function register_new_custom_rewrite() {
	global $wp_post_types, $wp_rewrite;

	foreach ( $wp_post_types as $post_type => $options ):
		if ( $post_type != "podcast" ) continue;
		$wp_rewrite->add_rewrite_tag("%$post_type%", '([^/]+)', "post_type=$post_type&name=");
		$wp_rewrite->add_permastruct($post_type, "%year%%monthnum%/%$post_type%", false, EP_PERMALINK);
	endforeach;
}

add_action('init', 'register_new_custom_rewrite', 99);


/**
 * Replace %year% and %monthnum% in permalinks with the correct values
 *
 * @since 1.0.0
 */
function filter_post_type_link($post_link, $id) {
	$post = &get_post($id);
	$unixtime = strtotime($post->post_date);
	$post_link = str_replace('%year%', date('Y', $unixtime), $post_link);
	$post_link = str_replace('%monthnum%', date('m', $unixtime), $post_link);

	return $post_link;
}

add_filter('post_type_link', 'filter_post_type_link', 10, 2);