| 
<?php
 include_once './app/Mage.php';
 Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);
 
 $from = new DateTime('2020-01-01 00:00:00');
 $from = $from->format('Y-m-d H:i:s');
 
 $to = new DateTime('2020-12-22 23:59:9');
 $to = $to->format('Y-m-d H:i:s');
 
 $orders = Mage::getModel('sales/order')->getCollection()
 ->addFieldToFilter('status', 'complete_shipped')
 ->addAttributeToFilter('created_at', array('from'=>$from, 'to'=>$to));
 foreach ($orders as $order) {
 echo 'Updating status of order ' . $order->getId() . '<br>';
 $order->addStatusToHistory('complete', 'Status manually updated on ' . date("d - m - Y") . '.');
 $order->save();
 echo '----- Succedeed! ----- <br><br>';
 }
 
 exit();
 
 |