Advantages of Adding Date on your Blog:
One of the minor algorithms say that advanced visitors or crawlers such as Google, Yahoo and Bing are also aware of freshness and frequency of the website respectively.
Why Should SEO depend on Date?
Visitors today are more advanced and always want themselves to move along with the current situations and emotions of surroundings.
Example: We might not be more interested in development of your city in past but we are more towards current and future situations.
Search Engines, Crawlers
As we know about Google Panda and Google Penguin algorithms there are several updates happening in Search Engines every month to increase SERP usability and user satisfaction. Therefore crawlers have also taken fresh content or frequency of content change and new updates or articles as one of the factors for SERP Ranking.
Example: Articles written by popular blogs which are frequent such as SEOmoz, Mashable etc., rank higher because they have plently of fresh content such as Discovering Local Citation Opportunities - Whiteboard Friday, How to Use Creative Commons Visuals on Your Site respectively.
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