Robert_Charlton - 10:27 pm on May 21, 2013 (gmt 0)
On the Google Update thread, nwelsh posted that he believes we're seeing old data, and that he thinks it's a total reindex in progress...
Google Updates and SERP Changes - May 2013
12:59 pm on May 21, 2013 (PST -8)
Sorry we don't have a way of linking directly to a post, but the above might get you there.
I was thinking that it might be a confirmation reindex, run on a portion of the web, to compare results with seed sets prior to a complete reindex, but I'm now thinking it could well be a full reindex.
Regarding the date, new member rossell123 asked earlier...
So nobody knows what the update was that took place on 16th May 2013?
May 17th in Webmaster Tools is close enough to confirm this date, and I've added May 17th to the title of this thread.
For now, discussion should probably continue both here or in the May update thread, depending on the types of observations you have.