function change_event_slug_on_save( $post_id ) {
    if ( ! wp_is_post_revision( $post_id ) && tribe_is_event($post_id) ) {
        $post = get_post($post_id);
        $slug = sanitize_title($post->post_title);
        $newslug = $slug . '-' . tribe_get_start_date( $post_id, false, 'j F Y' );
        if ($post->post_name !== $newslug) {
            // verify post is not a revision, and an event
            // unhook this function to prevent infinite looping
            remove_action( 'save_post', 'change_event_slug_on_save' );
            // update the post slug
            wp_update_post( array(
                'ID' => $post_id,
                'post_name' => $newslug
            ));
            // re-hook this function
            add_action( 'save_post', 'change_event_slug_on_save', 10, 1 );
        }
    }
}

add_action( 'save_post', 'change_event_slug_on_save', 10, 1 );