If you login to your Google Search Console account and view many of the reports in there, you will get a notice at the top of many of the reports that says the data may be changed due to infrastructure updates. The warning is on a yellow background and reads:
Jan-22: Search Console performed an infrastructure update that may cause a change in your data. Learn more about Search Console data anomalies.
Here is a screen shot:
The thing is, when you go to the Search Console data anomalies page, there is nothing from January 22, 2017 listed there. There is the old Twitter if this means there was an algorithm update. NO! This is why Google changed the word update to note and I still get these questions.
Forum discussion at Twitter.