Modify query after meta value

Question

Here’s an example using WP_Query‘s meta_query to query posts between two meta key values:

$meta_query = array(
    array(
        'key' => 'event_date',
        'value' => array( $date_start, $date_end ),
        'compare' => 'BETWEEN'
    )
);

$args = array(
    'posts_per_page' => -1,
    'meta_key' => 'event_date',
    'orderby' => 'meta_value',
    'meta_query' => $meta_query
);

$results = new WP_Query( $args );