D Day is 21st April
Announced on the Google webmaster central blog: http://googlewebmastercentral.blogspot.co.uk/2015/02/finding-more-mobile-friendly-search.html
“Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.”
John Mu provides some good advice on mobile in a recent Google webmaster hangout:
Check your website using this handy tool:
Just paste your URL in and Google will tell you if that page is mobile friendly.
Also check in your WMT account – old HTML pages may be lurking that are not mobile friendly; it is easy to forget about orphan pages if they are no longer needed, but Google might still judge your site on them.
The update will probably roll out over a week or so.
Report changes below and if you lose traffic after the update feel free to ask for some advice here, or head to the Google forums.