aristotle - 6:56 pm on Oct 15, 2012 (gmt 0)
Throughout the summer they were around 100k impressions. Now, Oct 18, they went up to 450k impressions.
One of us must have looked at our calendar wrong. I didn't think Oct 18 had arrived yet. I believe the last penguin refresh was Oct. 5. Is that the day you're thinking about?