Sort events in descending order in WordPress

In the wp_posts table, the data looks like this:

and when I insert an event, in addition to this table, goes data to wp_postmeta , and looks like this:

inthefilethatdisplaystheeventslookslikethis:

<divclass="latest-events">

                <?php query_posts('post_type=event&posts_per_page=3'); if (have_posts()) : while (have_posts()) : the_post(); ?>

                    <article class="latest-event cf">

                        <?php if(ale_get_meta('event_date')) { ?>

                            <time datetime="2014-08-09" class="date">

                                <?php $date_event = ale_get_meta('event_date');

                                $date_event_one = explode('/',$date_event); ?>

                                <span class="date__day"><?php echo date("d", mktime(0, 0, 0, $date_event_one[0], $date_event_one[1], $date_event_one[2])); ?></span>

                                <?php echo date("M", mktime(0, 0, 0, $date_event_one[0], $date_event_one[1], $date_event_one[2])); ?>

                                <span class="date__year"><?php echo date("Y", mktime(0, 0, 0, $date_event_one[0], $date_event_one[1], $date_event_one[2])); ?></span>

                            </time>

                            <!-- End date -->

                        <?php } else { ?>

                            <time datetime="2014-08-09" class="date">

                                <span class="date__day"><?php echo get_the_date('d'); ?></span>

                                <?php echo get_the_date('M'); ?>

                                <span class="date__year"><?php echo get_the_date('Y'); ?></span>

                            </time>

                            <!-- End date -->

                        <?php } ?>



                        <div class="latest-event__wrap">

                            <header class="latest-event__header">

                                <h1 class="latest-event__title">

                                    <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>

                                </h1>

                                <?php $cur_terms = get_the_terms( $post->ID, 'event-category' );

                                if($cur_terms != '') { ?>

                                    <p class="latest-event__category">

                                        <?php

                                        foreach($cur_terms as $cur_term){

                                            echo ' '. $cur_term->name.' ';

                                        }

                                        ?>

                                    </p>

                                <?php } ?>

                            </header>

                            <!-- End event post header -->

                            <p><?php trim_content_chars(120,'...') ?></p>

                        </div>

                        <!-- End event post wrap -->

                        <a href="<?php the_permalink(); ?>" class="btn-more">+</a>

                    </article>

                    <!-- End event post-->

                <?php endwhile; else: ?>

                    <?php ale_part('notfound')?>

                <?php endif; wp_reset_query(); ?>

            </div>

            <!-- End Events posts -->

How to display events in descending order, with event date going to table wp_postmeta , in field meta_value ?