Allow 'bracketing' of tweets between CC license changes or updates.

It would be great if TweetCC could track the most recent CC license change. For instance, I tweet @tweetcc with a particular license A (at time X) so all subsequent tweets are under this license. Then I tweet @tweetcc a more restrictive license B (at time Y) which applies to subsequent (not previous) tweets. I can then later revert to the less restrictive license A (at time Z) with the final result being that tweets before time Z are unlicensed, between time Y and Z are more restricted (license B), and between X and Y (and after Z) are licensed under A.