Reporting when answers are Public

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I want to be able to report when an answer is created, and again when the answer is set to Public.  We refer to this change as being published, which often differs from the date the answer was public.  I am able to create the report to tell me when the answer was created very easily, but does any one know if there is a standard field that we could query that would show the date of publish?

In a previous conversation, it was mentioned that it could be in the transactions table, but I was unable to find that out for sure.  Wondering if anyone else has had any luck on this.