brinked - 10:51 pm on Dec 19, 2011 (gmt 0)
synthese, I cant really give a definite timeline. The changes that were made to these sites were gradual and not all made in one day. I would say a little less than 2 months after they started applying the changes.
One site that I recovered took about a week and had over a 300% increase in traffic from before the penalty so that was huge. In that case I believe it was an over op penalty and not related to panda.