Change Order Date when changing an order - magento

Question

I'm hoping someone will be able to solve an issue that takes us a lot of manual labour, the solution seems simple :-)
Summary:
Is it possible to change the code that, when you Edit an order (invoiced or not yet invoiced) that is does not take the Order Date and Time of when you edited the order, but it uses the Order Date and Time of the original order?
Example:
Order 1000 was placed on 15/05/2015 at 12:00
Order 1000 was edited on 25/05/2015 at 14:00, the new order ID is 1000-1
We will credit or cancel order 1000, depending on the invoice state
Standard Magento will give order 1000-1 the Order date of 25/05/2015 14:00
But we would like order 1000-1 to receive the order date of 15/05/2015 12:00, the same as original order 1000.
Explanation:
We use a Magento Extension (Embedded ERP) which uses product reservations. If a customer orders a product, it does not remove the item from stock, but reserves stock. If the item is on backorder, the customer is placed in queue.
The system uses a first in, first out system. It uses the order date to check which customer is higher in queue than the other customers.
Because we use backorders, customer sometimes like to add or remove items to order, because they have to wait for items anyway. But when changing an order to add or remove items, the new order gets a new Order Date and Time. We want the customer to have the same product reservations as their original order. So now we manually change the product reservation of each item so it's the same as their original order.
I expect we can have the correct product reservations on the new order done automatically when the new order has the same order date and time of the original order.

Answer 1

Copy the file app/code/core/Mage/Adminhtml/Model/Sales/Order/Create.php into app/code/local/Mage/Adminhtml/Model/Sales/Order/. Keep the folder structure unchanged!
Find the option createOrder() and change this
if ($this->getSession()->getOrder()->getId()) {
$oldOrder = $this->getSession()->getOrder();
$this->getSession()->getOrder()->setRelationChildId($order->getId());
$this->getSession()->getOrder()->setRelationChildRealId($order->getIncrementId());
$this->getSession()->getOrder()->cancel()
->save();
$order->save();
}
with this:
if ($this->getSession()->getOrder()->getId()) {
$oldOrder = $this->getSession()->getOrder();
$this->getSession()->getOrder()->setRelationChildId($order->getId());
$this->getSession()->getOrder()->setRelationChildRealId($order->getIncrementId());
$this->getSession()->getOrder()->cancel()
->save();
$order->setCreatedAt($oldOrder->getCreatedAt());
$order->save();
}