title: Extract year and month from a timestamp using regex java
body: <p>I need to extract the year and month from an  timestamp using regex.</p>
  
  <p>Example :</p>
  
  <p>I have a  timestamp: <code>20130923161057</code>. I need to extract the year <code>2013</code> and month <code>09</code> using regex.</p>