Modify taxonomy.php to filter for custom date field value

    $today = date( 'Y-m-d' );

    $term = $wp_query->query_vars['term'];

    $args = array(
            'post_type' => 'bgmp',
            'tax_query' => array(
                array(
                    'taxonomy' => 'coupon',
                    'field' => 'slug',
                    'terms' => $term
                )
            ),
            'meta_query' => array(
            array(
                    'key' => 'coupon_end_date',
                    'value' => $today,
                    'compare' => '>=',
                    'type' => 'DATETIME'
            )
            )
            );
        $the_query = new WP_Query( $args );