title: Replace values in pandas series where the element to be replaced contains a part of the element by which it is to be replaced
body: <p>For example I want to replace <code>2/8/2014 0:00</code> with <code>2014</code> and <code>1/29/2015 0:00</code> with <code>2015</code> and henceforth.</p>
  
  <pre><code>2014               180657
  2015               153837
  2014                72395
  2012                69708
  2013                61364
  2015                54117
  2013                 3313
  2012                 1076
  2/8/2014 0:00           2
  7/3/2014 0:00           2
  1/29/2015 0:00          2
  9/1/2014 0:00           2
  11/22/2014 0:00         2
  10/16/2014 0:00         2
  </code></pre>