I was just reading the latest post by search engine land and one part of a post jumped out at me

Date Detection

On a somewhat similar note, the update also says that Google has improved how it detects the date of a web page (document), and that means searchers should see “fresher, more timely results, particularly for pages discussing recurring events.”

I have always removed the dates from my niche blogs so that the posts do not look old to anyone who comes upon them. But in the early days of a post would we do better to actually include the date so Google can see it is brand new and push it up the rankings. Of course you would then want to remove the date so people do not see a post with a date 2 years in the past, old info is not always bad info but with the Internet changing so fast people tend to ignore older posts and look for more recent items.

This was not the only update that Search Engine Land mentioned but it was the one that caught my eye. You can read more on their site

http://searchengineland.com/googles-january-search-update-110121