How i change order status automatically to "completed" from "delivered" after 15 days in wordpress woocommerce site

I'm using the custom order statuses plugin for custom order status.

our shop has 15 days return policy.

so, I want to change the order status "Delivered" to "Completed" after 15 days. it means when change status Delivered that time to 15 days later automatically changes order status to "Completed"

I tried the code below but not working for me.

function setCompletedAfter15Days(){
    $orders = wc_get_orders( array(
            'status' => 'delivered',
            'date_created' => '<' . ( time() - 15 * DAY_IN_SECONDS ),

    ) );

    foreach ($orders as $order){
        $order->update_status( 'completed' );
    }} wp_schedule_event( time(), 'daily', 'setCompletedAfter15Days' );