get_the_date will not work with child pages

I woud like to create a list of child pages. all of the same parent. But I would like to insert the Year at the top of each section as appropriate. For example:

2012

Child page 1
Child page 2
Child page 3

2011

Child page 1
Child page 3
Child page 3

I have tried the following code, but the get_the_date(‘Y’) function always returns the year of the parent page and not the child pages. However, the child pages correctly display in a long uninterrupted list. How do I change the value of $this_year so that I can display the appropriate years as above?

$query = new WP_Query( array(
		'post_type' => 'page',
 		'post_parent' => '263',
 		'posts_per_page' => '-1' ) );
$prev_year = NULL;

// Loop
while($query->have_posts()):
     $query->next_post();
     $id = $query->post->ID;
      $this_year = get_the_date('Y');
      // echo '<h3>' . $this_year . '</h3>';
      if ($prev_year != $this_year) {
          // Year boundary
          if (!is_null($prev_year)) {
             // A list is already open, close it first
             echo '</ul>';
          }
          echo '<h3>' . $this_year . '</h3>';
          echo '<ul>';
     }
     echo '<li>';
     echo get_the_title($id);
     echo '</li>';
     $prev_year = $this_year;
endwhile;
   echo '</ul>';

My site is currently on my localhost.
Thank you.