title: Function to determine first day of a month, last day of a month, etc.
body: <p>I'm creating a scheduler and need to be able to do the following in C#:</p>
  
  <ol>
  <li>Find the 1st Tuesday of June 2012   </li>
  <li>Find the last Friday of March 2008  </li>
  <li>Find every Saturday in January 2013 </li>
  <li>Find the 3rd Friday in July 2009   </li>
  <li>Find every Saturday over the next 3 months</li>
  <li>Find every day in March 2018</li>
  </ol>
  
  <p>The results should come back as <code>DateTime</code> or <code>List&lt;DateTime&gt;</code>.</p>