Search results, like warm cookies right out of the oven or cool refreshing fruit on a hot summer’s day, are best when they’re fresh. Even if you don’t specify it in your search, you probably want search results that are relevant and recent.
If I search for [olympics], I probably want information about next summer’s upcoming Olympics, not the 1900 Summer Olympics (the only time my favorite sport, cricket, was played). Google Search uses a freshness algorithm, designed to give you the most up-to-date results, so even when I just type [olympics] without specifying 2012, I still find what I’m looking for.
Given the incredibly fast pace at which information moves in today’s world, the most recent information can be from the last week, day or even minute, and depending on the search terms, the algorithm needs to be able to figure out if a result from a week ago about a TV show is recent, or if a result from a week ago about breaking news is too old.