Wrap group of wp query posts to parent div by date/year

Question

I have wp query for posts. I'm ordering them by custom field "event_date". (The field format example is 09.08.2016). I'm extracting year and month from each post and adding it as div class, however i want to wrap all posts by parent div for each month. At frontend i want it to have like this:

<div id="082016">
  <div class="post 082016"><?php the_title();?></div>
  <div class="post 082016"><?php the_title();?></div>
  <div class="post 082016"><?php the_title();?></div>
</div>
<div id="092016">
  <div class="post 092016"><?php the_title();?></div>
  <div class="post 092016"><?php the_title();?></div>
</div>
<div id="102016">
  <div class="post 102016"><?php the_title();?></div>
  <div class="post 102016"><?php the_title();?></div>
  <div class="post 102016"><?php the_title();?></div>
</div>

And so on. Is it possible to wrap all posts to such parent div? How should i do it?

<?php 
$args = array(
  'posts_per_page' => -1,
  'post_type' => 'event',
  'meta_key' => 'event_date',
  'orderby' => 'meta_value_num',
  'order' => 'ASC'
);

$wpquery = new WP_Query($args); ?>
<?php while( $wpquery->have_posts() ): $wpquery->the_post();  ?>
    <?php
    $date = get_field('event_date'); 
    $year = date('Y',strtotime($date)); 
    $month = date('m',strtotime($date)); 
    $day = date('d',strtotime($date));
    ?>
    <div class="<?php echo $month; echo $year;?>">
        <h1><?php the_title();?></h1>
    </div>
    <?php endwhile; ?> 
<?php wp_reset_postdata(); ?>

Many thanks for any help!

Answer 1

This cannot be done only by querying database. Firstly, you have to iterate through all items and create array of posts grouped by dates.

$args = array(
    'posts_per_page' => -1,
    'post_type' => 'event',
    'meta_key' => 'event_date',
    'orderby' => 'meta_value_num',
    'order' => 'ASC'
);

$wpquery = new WP_Query($args);
$posts = $wpquery->get_posts();
$ordered_posts = array();

foreach ($posts as $post) {
    $meta_value = get_post_meta($post->ID, 'event_date', true);
    if (!$meta_value) {
        continue;
    }
    $date = date('mY', strtotime($meta_value));
    $ordered_posts[$date][] = $post;
}

Next, you have to iterate through grouped array to display divs as you want:

foreach ($ordered_posts as $post_date => $posts) { ?>
    <div id="<?php echo $post_date; ?>">
        <?php foreach ($posts as $post): ?>
            <div class="post <?php echo $post_date; ?>">
                <?php echo $post->post_title; ?>
            </div>
        <?php endforeach; ?>
    </div>
<? }