When you update information on your site it does not automatically update instantly in Google's index. Rather, Google's index is updated approximately once a month.
It's surprising that it takes them a whole month to update the links in the directory! I was not expecting this from a company like Google.

Here are a few webmasters around the world have to say about this process..

1. I'm having an issue with caching - I have corrected a problem on my site but it doesn't appear to have been corrected within Google. How often do you guys update? it's been fixed for nearly 3 weeks now...
   for shame.
2. I had my website modified before the apparent update (I assume it happened on August 15th looking at other websites) and my website did not update - it still has the dead links cached, and shows no update date under my description (which is incorrect as of now). Why is this happening, why do some sites not get updated and others do? When will my new site get updated?
3. Google seems to keep cached pages a long time. I have completely redone my site. How can I get them to update my site?
4. Prior to December 15th we had a construction site page up at our URL (flagpal.org). On Dec. 15th we published a 32-page web site, replacing the construction page with our new home page. As of today, January 1st, a Google search of our URL still brings up the construction page information. Is there a way to get Google to revisit the page and change the description?

Here is the explanation from one of the Google Experts:
Google indexes over 2 billion URLs on each crawl now, so it updates once a month and it can take from one to eight weeks to get listed if you have links from other sites that are already in Google.

Simply "not expectable". I will like to see the latest information instead of browsing through the Google Cache. I have updated my website around 15 days back and even today if I type shantanu oak in the Google search, I am getting the cached pages from my old site!