title: regex for extracting date from string
body: <p>I have the following date string - <code>"2013-02-20T17:24:33Z"</code></p>
  
  <p>I want to write a regex to extract just the date part <code>"2013-02-20"</code>. How do I do that? Any help will be appreciated.</p>
  
  <p>Thanks,
  Murtaza</p>