title: Pipe string to GNU Date for conversion - how to make it read from stdin?
body: <p>GNU Date lets you convert date strings like so:</p>
  
  <pre><code>$ date +"%d %m %Y" -d "yesterday"
    04 01 2012
  </code></pre>
  
  <p>Is it possible to pipe a date string to it for conversion?  I've tried the obvious <code>-d -</code> like so:</p>
  
  <pre><code>$ echo "yesterday" | date +"%d %m %Y" -d -
  </code></pre>
  
  <p>but it prints today's date instead of yesterdays.</p>
  
  <p>Is it possible to pipe values to it or doesn't it support that?</p>
  
  <p>Thanks.</p>