I started noticing that for some search results by google, there is a x hours ago before the description under the link. How does google determine this?There is also this link Get more results from the past 24 hours. How does this work? Is that based on last crawl timestamp? if so, how can one make google crawl a dynamic site more frequently? should we set that in HTTP headers like last-modified?
Google search results now shows last updated for some results. How does it work?
google search