For example, take a look at How do I get the local internet IP address?. You can see when the question was posted, but there's no similar information on the answers provided.
Since it's possible to find answers via Search, it seems like this would be useful information, especially if an answer is contributed well after the original question.
This can be handled as simply as the root question handles it, e.g. Answer: <title> contributed by <whoever> on <whenever>.
Just a thought...
P.S. FTR, I did use Super Search to see if the idea had been submitted previously, but didn't find anything directly relevant. Of course, I may have missed it.