title: How to parse year from a date in r
body: <p>I have 53000 Date data-set and I want to extract only "year" from the date variable.
  Do you guys know how can I do this?
  My data are as follows:</p>
  
  <pre><code>OPN_DT_TM
  18/07/2003 10:55
  12/06/2004 6:00
  9/06/2007 12:20
  29/06/2001 16:00
  6/06/2000 7:55
  27/11/2006 10:15
  17/11/2001 17:00
  12/05/2004 22:00
  16/04/2005 22:00
  18/03/2005 8:40
  13/06/2006 11:10
  30/07/2006 12:00
  16/07/2002 6:10
  16/07/2002 7:15
  3/09/2004 6:00
  9/11/2004 15:20
  25/08/2005 14:15
  24/11/2001 19:10
  15/04/2002 6:30
  20/06/2002 6:30
  17/03/2003 7:00
  15/01/2005 13:00
  23/03/2007 1:00
  21/01/2001 10:30
  ,,,
  </code></pre>