Sometimes you want to add one custom column for post or custom type posts like when you added some post meta values and want to show it in post list then you found that you have no way to add that through wp-admin files.
It’s just a simple function.php work. You just need to work on code to add extra column in post list.

    // ADD NEW EXTRA COLUMN
    function postauthorDOB_columns_head($defaults) {
        $defaults['author_dob'] = 'Authors DOB';
        return $defaults;
    }

    function postauthorDOB _columns_content($column_name, $post_ID) {
        if ($column_name == 'author_dob') {
$meta_values = get_post_meta( $post_ID, 'author_dob');
Echo $meta_values ;
      }
    }

add_filter('manage_posts_columns', ‘postauthorDOB _columns_head');
add_action('manage_posts_custom_column', ‘postauthorDOB _columns_content', 10, 2);