title: Wordpress WP_Query compare only Month part of meta_query key
body: <p>i have been trying to use wordpress wp_query method, but my case is specific.</p>
  
  <p>I need to select all product of the current month so here is my code</p>
  
  <pre><code>$args = array(
      'numberposts' =&gt; -1,
      'post_type' =&gt; 'product',
  
      'meta_query' =&gt; array(
              'Relation' =&gt; 'AND',
      array(
              'key'     =&gt; 'wpcf-product_status',
              'value'   =&gt; 'valid',
              'compare' =&gt; '='
          ),
      array(
              'key'     =&gt; 'wpcf-product-start_date',
              'compare' =&gt; '=',
  
              'date_query' =&gt; array(
                  array(
                          'month'      =&gt; date('m'),
                          'compare'   =&gt; '=',
                  ),              
          ),
      ),
      ),
  );
  // get results
  $the_query = new WP_Query( $args );
  </code></pre>
  
  <p>I can not get the exact result.
  how is it possible to test only the date MONTH like it is done is SQL (<code>WHERE MONTH(wpcf-product-start_date) = MONTH(NOW())</code>)</p>
  
  <p>any idea please?</p>