Code-Snippets-Functions/Execute a function on a child site/WooCommerce/add-an-expiration-date-to-orders-based-on-order-items-count.txt

add_action( 'woocommerce_checkout_create_order', 'add_expiration' );
function add_expiration( $order, $data ) {
    $items_count  = WC()->cart->get_cart_contents_count();

    $order->update_meta_data('expiration_date', date( 'Y-m-d H:i:s', strtotime( '+'. ( $items_count * 15 ) .' days' ) ) );
}