Change the sort order of subpage list

I have managed to research, find and modify some code here in the forums to display a list of child-pages with a thumbnail from that page and a description of the page. It has defaulted to ordering it by newest creation date. how do I make this order by oldest creation date first?

Here is the code I am using:

<?php
$child = $post->ID;
$args=array(
  'post_parent'=> $child,
  'post_type' => 'page',
  'post_status' => 'publish',
  'posts_per_page' => -1,
  'caller_get_posts'=> 1,
  );
$my_query = null;
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
  echo '';
  while ($my_query->have_posts()) : $my_query->the_post(); ?>
<div id="pp-wrapper">
<div id="pp-thumb">
<a href="<?php the_permalink() ?>"><img src="<?php echo get_post_meta($post->ID, 'Featured_Image', true); ?>" width="200px"></a></div>
<div id="pp-title">
<a href="<?php the_permalink() ?>"><font color="#333"><?php the_title(); ?></font></a>
</div>
<div id="pp-description">
<?php
    $name = get_post_meta($post->ID, 'Post_Description', true);
    if ($name){
      echo ''.$name .'</div></div>';
    }

endwhile;
}
wp_reset_query();  // Restore global post data stomped by the_post().
?>

I don’t know enough about php to decipher the instructions in the codex. The more I modify code the more I learn about its structure and how to write from scratch. But I’m still a noob all things considered.

Thanks for any help that can be provided.