A Search Engine Roundtable post, reports the thread over at WebmasterWorld discussing an updated Google patent named Information retrieval based on historical data, which highlight following two out of several abstracts:

1. How does Google know when a site has changed enough where they should drop all the past trust and link popularity associated with that site?
2. We heard it before, "Don't get links too quickly" because it seems unnatural. Well, here it is on paper.

According to Google itself:

Stale content refers to documents that have not been updated for a period of time and, thus, contain stale data (documents that are “no longer updated, diminished in importance, superceded by another document“).

Bill Slawski summarizes the patent:

The Constitution of the United States is an old document, but it’s not stale. A news article about the “World Series” from 1918 may not be what a baseball fan wants to see when searching for “World Series” this October.

Full Article

Source:→ SEJ