There is a date and time updated field

Yes, but I am seeing that there is only the "last" date updated. Could have been updated to Invoice. I need to know when it updated from Quote to Sales Order. Thanks!

Or could have added/removed products-changed pricing etc. That action would also be an update.

In current versions, Sales Order History Header has a Promoted Date which is the date the order was converted from a quote to an order. There is an option in Sales Order Options to retain Sales Order History.
New version 2016 enhancements include:
Default Expiration Date for Quotes
Can now promote quotes to back orders, master orders, and repeating orders.
Use Default Order Date When Promoting Quotes

So it is only available in the 2015 and 2016 versions correct? We have 2014. I am assuming there is no way to determine the "promotion" date in 2014?

That is correct jlr2. This is one of the added features in verison 2015 product update 1.
To see all new features, access the knowledgebase and search on "what's new 2015" for example. Select the Customer upgrade guide or the Download version....., then select the download link. In the actual download page see the attachments or related resource links to the pdf which provides all of the new features.

Thanks so much for your help!

You are welcome. I forgot to add that the only workaround until you upgrade might be to add a UDF but without some sort of scripting it would probably be entered manually by the user.