wordpress the_date(‘d F y’) not working in query_posts

in my template I want to show and specific category posts in side bar (cat = 17) so I use this code :

<?php $cat=17; ?>
<?php $pp = query_posts("cat=$cat&showposts=3"); ?>
<?php if( $pp )
    { 
?>
        <section class="sidebar_boxes_container">
            <div class="sidebar_headers" > اطلاعیه ها &nbsp<img src="<?php bloginfo( 'template_url'); ?>/img/notification.png"></div> 
            <?php while (have_posts()) : the_post(); ?>
                <div class="notification_item" >
                    <span class='thumbnail' > <?php if ( has_post_thumbnail() ) { the_post_thumbnail('small_thumbnail');} ?> </span>
                        <a href="<?php the_permalink(); ?>"> <h5><?php the_title(); ?> </h5></a>     
                        <div  style='width:100%'>
                            <div class='noti_divs' >
                                <img src="<?php bloginfo( 'template_url'); ?>/img/calender.png"><?php the_date('d F y') ;?>
                            </div>
                            <div class='noti_divs' id="noti_divs_author">
                                <img src="<?php bloginfo( 'template_url'); ?>/img/author.png"> 
                                <?php the_author_posts_link();?>
                            </div>
                        </div>                                    
                        <?php the_excerpt(); ?>
                </div>
            <?php endwhile;?>
        </section>
        <?php wp_reset_query(); ?>
<?php
    }  
else
    {
        echo "empty";
    } ?> 

all wordpress functions work well but the : <?php the_date('d F y') ;?> returns null for all ; while if I change the post category to another one , <?php the_date('d F y') ;?> returns true date in posts
what should I do ?