Google determines a date using a variety of factors, including but not limited to: any prominent date listed on the page itself or dates provided by the publisher through structured markup. Google doesn’t depend on one single factor because all of them can be prone to issues. Publishers may not always provide a clear visible date. Sometimes, structured data may be lacking or may not be adjusted to the correct time zone. That’s why Google’s systems look at several factors to come up with what they consider to be their best estimate of when a page was published or significantly updated. To help Google to pick the right date, site owners and publishers should show a clear date and use structured data:
Google’s John Mueller said on Reddit this morning that he believes that all sites running a separate mobile URL for their mobile site solution should work on moving those implementations to a responsive site design instead. He said that mostly because it makes it easier to maintain, not because of any SEO benefit. John wrote “at some point all of these sites with separate mobile URLs should just move to a responsive design anyway, which makes all of this moot. (Separate mobile URLs makes everything much harder than it needs to be).”
Google on Wednesday confirmed that it released a broad core search ranking algorithm update this week. “Our guidance about such updates remains as we’ve covered before,” the company said. Google Search Liaison Danny Sullivan confirmed this update started March 12.