Panda 4.0: Google Algorithm Update May 2014

Every time Google algorithm update happen it big like Panda Update 4.0 then it's too painful for spammers and some good webmasters they don't know about spam lol.
This is so sorry news for those webmasters, Google official's mattcutts said, Google is rolling out our Panda 4.0 update starting today.
below is the embeded tweet of mattcutts,

Actually when this Panda 4.0 update happen?

Google web spam team officials mattcutts tweet just now 21st may 2014 about the panda 4.0 algorithm is rolled out. But previously the update happens because the attached image will explain everything. Mozcast explains heavy weather change over to 98dergree in 19th may.
Algoroo shows big variation in the search position for the past 4 days. so panda 4.0 already rolled out before mattcutts mentioned. Previously Google officials are telling there is nothing is going on but the Update is already rolled out.
After a hour Mattcutts tweets mentioned about the spammy queries,