Welcome to the Community, RML9.

I'm here to share some information about the expected delivery date of the purchase order.

You're right that QuickBooks Desktop uses the purchase order date as the expected delivery date. If you want to change it, you'll have to open the purchase order and manually update it.

Here's how:

1. Open the purchase order.
2. Update the Expected date (refer to the screenshot below).
3. Click Save & Close.

Check out this link for more details: Create a purchase order.

That information should get you on the right track. The Community always has your back, so don't hesitate to let me know if you have any questions. Have a good one.