Wordpress Query using custom fields with Meta Box (http://wordpress.org/plugins/meta-box/) date fields to sort.

wp-query-events-orderby-date.php

<?php $query = "
    SELECT * FROM $wpdb->posts
    LEFT JOIN $wpdb->postmeta ON($wpdb->posts.ID = $wpdb->postmeta.post_id)
    WHERE ($wpdb->posts.post_status = 'publish') AND
    ($wpdb->postmeta.meta_key = 'event_start_time')
    ORDER BY $wpdb->postmeta.meta_value ASC";
    $events = $wpdb->get_results($query, OBJECT);
  ?>
<?php if ($events): foreach ($events as $post): ?>
  <?php get_template_part( 'loop', 'event' ); ?>
<?php endforeach; endif; ?>