Order posts in Admin by date published?

I recently did a batch update to posts in order to change the Author. However, now all the posts in my Admin area are listed by Date Modified — which is the same for all posts (because I batch modified them).

How can I get this back to displaying posts by newest first according to Published Date?

I’ve searched around and can’t find anything that describes this problem.

I tried adding this to my functions.php, but it didn’t work …

/* Sort posts in Admin area. */
function custom_post_order($query){
    $post_types = get_post_types('', 'names');
    /* The current post type. */
    $post_type = $query->get('post_type');
    /* Check post types. */
    if(in_array($post_type, $post_types)){
        /* Post Column: e.g. title */
        if($query->get('orderby') == ''){
            $query->set('orderby', 'post_date');
        }
        /* Post Order: ASC / DESC */
        if($query->get('order') == ''){
            $query->set('order', 'DESC');
        }
    }
}
if(is_admin()){
    add_action('pre_get_posts', 'custom_post_order');
}

It’s a modified piece of code from this post.

Thanks!