Like other search engines, Google already distinguishes between various types of content. You can search specifically for images, videos, books, blog posts, and so forth. Google has separate search engines for each. But two recent changes suggest that Google is improving its ability to classify different types of content that’s gathered from ordinary web pages. Search Engine Roundtable points to a discussion on WebmasterWorld about the addition of dates at the beginning of some search results — something Michael Gray spotted in mid-September. From my personal experience, this seems to be happening mostly on content that Google can identify as blog posts and news articles — but not exclusively on those types of content.
And speaking of identifying types of content, Google Operating System points out that Google is starting to show special forum-related information in search results when it can identify that the result comes from a message board. Author Alex Chitu suggests this could mean new advanced search options in the future:
This new feature shows that Google is able to automatically classify web pages and to extract relevant information. Once Google starts to show data for other kinds of web pages, we can expect to see an option to restrict the search results to a certain category (forums, reviews, blogs, news articles).
The screenshot above has examples of both cases, the top showing dates in the snippets, and the bottom showing forum information.