WP Group posts by year(desc) > month(desc) > date(asc)

Question

I have a custom category template to group posts by a custom field 'event_date'. 2 things I cannot figure out, correctly: grouping by year and month, and having those in descending order, while the posts themselves are in ascending order. Currently this will create an 'event-year' div and 'event-month' for each post. I'm assuming I'll need some for/each statement for each 'year' and 'month.' But, I just don't have the experience to write it up correctly.

so the final markup would be:

<div event-year>
    <div event-month>
        <article>
        <article>
    </div>
    <div event-month>
        <article>
    </div>
    <div event-month>
</div>
<div event-year>
    <div event-month>
        <article>
        <article>
    </div>
</div>

This is what I have now:

<?
$the_query = new WP_Query( array(
            'post_type'   => 'post',
            'post_status' => 'publish',
            'meta_key'    => 'event_date',
            'orderby'     => 'meta_value'
        ) );

        $current_header = '';
        $current_year = '';
        $current_month = '';
        $current_day = '';

        # The Loop
        while ( $the_query->have_posts() ) :
            $the_query->the_post();

            # get the event date
            $temp_date = get_post_meta( get_the_ID(), 'event_date', true );

            Break up the date format
            $dateTime = DateTime::createFromFormat("Ymd", $temp_date);

            if ( is_object($dateTime) ) {
              $month = $dateTime->format('F');
              $year = $dateTime->format('Y');
              $day = $dateTime->format('d');
              //...
            }

            $display_month = substr($month, 0, 3); 

            if($year != $current_year) {
                $current_year = $year;
                echo "<div id='event-year' data-year-group='$year'>";
            }

            if($month != $current_month) {
                $current_month = $month;
                echo "<div class='event-month'><h2>$year - $month</h2>";
            }
?>
    <article> post stuff in here... </article>
<? endwhile; ?>

Answer 1

$last_month = null;
$args = array(
    'post_type' => 'post',
    'orderby' => 'meta_value',
    'order' => 'DESC',
    'post_status' => 'publish'
);

$the_query = new WP_Query($args);

while ( $the_query->have_posts() ) :
    $the_query->the_post();
    $the_month = get_the_time( 'Ym' ); // e.g. 201611

    if ( $last_month !== $the_month ) {
        if ( $last_month !== null ) {
            // Close previously opened <div class="row" />
            echo '</div>';
        }

        echo '<br/><div class="row '.get_the_time("Y").'" >';
        echo 'MOnth: '.get_the_time('m');

    }

    $last_month = $the_month;

    ?>

    <div class="col-3">
        <?php the_title(); ?>
    </div>

    <?php

    if ( $the_query->current_post + 1 === $the_query->post_count ) {
        // Last item, always close the div
        echo '</div>';
    }

endwhile;