As a lawyer, I early recognized this problem with Word's automatic default date. You have had the issue in Word 2003 even if you didn't recognize it. The date field function (and that of related fields) has not changed since at least Word 97, and I suspect, not since Word 2. (Word 2003 is Word 11.) Word never knows when you are finished with a document. Only you would know that. There are a number of reasons for an experienced user to be unhappy with the ribbon versions of Word, but the DATE field and the way it acts is not one of them.
Using Date Fields in Microsoft Word

• I use the CreateDate field, as originally suggested, in my templates. you can update this field to a later date by using SaveAs and then updating the field.
• Another alternative would be to select the date field when you have completed your document and pressing either Ctrl+6 or Ctrl+Shift+F9 and unlinking the field (changing it from a field to text).
• A third alternative, and the one that I believe gives the greatest evidentiary value, is to convert the document to pdf format. This can be done directly or by scanning a printed copy.

In an existing document, changing the DATE field to a CREATEDATE field will give you a better approximation of of the date that the document was finalized.