title: Summing weekly data by month and year
body: <p>I have an excel 2007 file with data of weekly values for two years. I want to collate this into a cumulative monthly sum, but also bare in mind the year. For example, If I had the following dates:</p>
  
  <pre><code>6 Apr 13
  13 Apr 13
  20 Apr 13
  27 Apr 13
  4 May 13
  .
  .
  .
  .
  .
  12 Apr 14
  19 Apr 14
  26 Apr 14
  3 May 14
  10 May 14
  17 May 14
  24 May 14
  .
  .
  .
  .
  14 Feb 15
  21 Feb 15
  28 Feb 15
  7 Mar 15
  14 Mar 15
  21 Mar 15
  28 Mar 15
  </code></pre>
  
  <p>And I wanted to get the summed totals for the following periods:</p>
  
  <pre><code>April 2013
  May 2013
  June 2013
  July 2013
  .
  .
  .
  .
  April 2014
  May 2014
  June 2014
  .
  .
  .
  January 2015
  February 2015
  March 2015
  </code></pre>
  
  <p>What would be the best way to go about doing so? I was thinking to use Sumifs, but was uncertain how well Month() and Year() play if the function was written like <code>sumif(...Year(...Month(..)))</code>.</p>