How do I know which person changed the due date on an assignment/quiz

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A quiz in a course had it's due date changed from Feb 18th to March 30th.    The teacher insists that they didn't do it, and what I can see in PageViews corroborates this.    

There are no other teachers or TA or designers in this course, so I suspect either the teacher was hacked, or someone with admin privileges to the subaccount made the change.

How can I see who or what changed the due date on this Assignment/Quiz ?   

(The change took place prior to April 20, which was the last time our test instance was refreshed, the due date change is already reflected in the test environment)

Thanks, Glen