$args = array('posts_per_page' => -1, 'orderby' => 'date' );

$myQuery = new WP_Query($args);

$date = '';

if ( $myQuery->have_posts() ) : while ( $myQuery->have_posts() ) : $myQuery->the_post();

if ( $date != get_the_date() ) {
    echo $date;
    echo '<hr />';
    $date = get_the_date();
}

the_title(); // or whatever you want here.
echo '<br />';

endwhile; endif;
wp_reset_postdata();