Google's Nathan Johns from the search quality analyst team at Google, said at the AMA with Google at SMX last week that Google officially began rolling out the core algorithm update on March 7th. We thought it was closer to March 9th and some felt it was closer to March 8th but no one thought it was March 7th - of course, we got time zone things playing into this.
Of course, the core update has been rippling through the search results for over a week now but it may be slowing down right now.
As I covered in my AMA post at Search Engine Land, Nathan from Google said this is designed to "reward under-rewarded sites,” and if your site saw a drop, just keep working on making your site better, it does not indicate a penalty. So nothing new there.
But the only item of interest and new was the March 7th date
