“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
Google recently posted to they’re webmaster central blog illustrating how it determines what date it will use for your web page search result snippets.
In the past Google has been criticized for at times getting the dates wrong, so them using this blog to clarify and may help improve the process.
The date for the search snippet is typically found above the search snippet located under the listed URL Google shows the date of a web page when its algorithms believe its relevant to include in the snippets and only shown when Google detects time sensitive, news-oriented, or new recognized content.
Google clears this up by saying it “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 our systems look at several factors to come up with what we consider to be our best estimate of when a page was published or significantly updated.”
Now for the meat and potatoes of the blog which explains for site owners and publishers on how to specify a date on a page.
The process is simple to specify a date show a visible date prominently on the page, use structured data such as the datePublished and dateModified schema with the correct time zone designator for both accelerated mobile pages and non accelerated mobile pages, and to make sure to use the ISO 8601 format for dates.
Why you should care
There’s a possibility that your site can run into an issue where a reader may stumble upon old content that was unintentionally given an incorrect date within a Google search snippet which can confuse traffic and make your site look less credible.
Ensuring your page is compliant with search snippet best practices can help you avoid these potential negatives and keep your content snippets accurate.