CPT display order

function custom_agenda_order( $orderby ) {
    global $wpdb;

    // Check if the query is for an archive
    if ( is_archive() && get_query_var("post_type") == "my_custom_post_type" ) {
        // Query was for archive, then set order
        return "$wpdb->posts.post_date ASC";
    }

    return $orderby;
}

add_filter( 'posts_orderby' , 'custom_agenda_order' );