I suggest to download the package with source codes and find the following search term: 'PaidDate ='. There're just three places where it's set: 1. When order status is paid 2. When you capture order 3. When you just mark order as paid (admin area)
I apologize, I should have been more clear in my question. I have made several order which have been paid (using the fake credit card 4111.....). I would have thought that upon completing the order, that this would have been set. Currently, every completed order contains a NULL value in this field and I'm unsure why a date is not being set when the order is completed. I'll examine the code a bit more but if you can offer a quick insight that would be great.
p.s. I am having to export data for a fulfillment processor and one of the required fields is the data of the order. This seemed like the proper field to use since it would represent a completed order vs the CreatedOn field which does not necessarily represent a completed order. This is why I asked the question.