Hi Alan,
I tried that but there is no Unsubscribe Date listed in my columns. That may have been a field that your team added?
I ended up creating a new field --"Unsubscribe Date Time" and have set up a new smart campaign flow. Below is my formula.
If (Data Value Changes) Unsubscribed, new value is true --> Change Data Value of Unsubscribe Date Time (my newly created field) to {{system.dateTime}}.
This seems to be working for any new unsubscribes in the future. Bad news is I still don't have a solve for all of the people who unsubscribed in the past.