"Gamed quite easily" seems like a stretch, given that the target is definitionally not moving. The search engine is fundamentally searching an immutable dataset that "just" needs to be cleaned.

How? They have an index from a previous date and nothing new will be allowed since that date? A whole copy of the internet? I don't think so.... I'm guessing, like others, it's based on the date the user/website/blog lists in the post. Which they can change at any time.