title: Get quarter of year in ruby
body: <p>I know this methodes to get the beginning and ending of the quarter for a specific date:</p>
  
  <pre><code>@date.beginning_of_quarter
  @date.end_of_quarter
  </code></pre>
  
  <p>But how can i get the beginning ending of for eg. the 4 quarter of the year 2012? Without having to pass a date that is in the middle of the 4 quarter of 2012 to <code>end_of_quarter</code>? Thanks</p>