I have 200 closed changes and I need to add 1 piece of data, specifically, a date.  

How can I do it? 

I tried the IMPORT WIZARD for Change.

Using a dummy ID (CHG-100) and the changes sample CSV file.  Trying to modify only the title on this particular change I got this error:
(BTW: The  field "status" is not empty)
 

Attached is the CSV file that I'm using for this test.