1 Very serious fluctuations happened on 8-1-2016
On Friday 8th of January 2016 webmasters noticed serious changes in search engine rankings on Google. The Seo experts confirmed the same news. The fluctuations went on for days.
2 Google Confirmed a Core Algorithm update
Gary Illyes & John Mueller of Google confirmed on twitter that Google made a core algorithm update to its search engine. See also why Google traffic fluctuates widely.
3 It's not a penguin update
Most webmasters speculated that the update is related to penguin but Google's spokesmen denied that. They said it's a core algorithm update not related to penguin.
4 Webmasters believed it's connected to Panda
Some Webmasters and SEO experts believe that the latest update was a quality update that has some kind of connection to Google panda. See how Google panda works.
5 Panda is now a core ranking signal
In about the same time people knew from Google that Panda became a core ranking signal and so no further Panda announcements might be made. This is one reason why webmasters believed that the last update is connected to Panda.
6 Massive effect
Many webmasters reported serious decrease/increase of Google traffic as a result of this update.
7 Google said it's not panda
Gary Illyes of Google has said on twitter that this update has nothing to do with Panda or any other animals. See also why Google Panda Slaps many quality sites.
8 Panda is still not real time
Gary Illyes has also said that people got it wrong when they believed that Panda is now real time. Panda is now a core ranking signal but still doesn't run real time.
9 No final word
Just like many of Google's core updates no one has a final word on what really happened apart from what Google said.