title: Validate DateTime's are sequential by month
body: <p>I have a list containing 60 <a href="http://msdn.microsoft.com/en-us/library/system.datetime(VS.71).aspx" rel="nofollow noreferrer">DateTime</a> objects (sorted in ascending order) and need to validate that each date is 1 month greater than the previous one in the list.</p>
  
  <p>For example, the following list of dates would be valid because they increment by one month with none missing:</p>
  
  <blockquote>
    <p>Jan-2009<br> Feb-2009<br> Mar-2009<br>
    Apr-2009<br></p>
  </blockquote>
  
  <p>However, the following list of dates would be invalid because Feb-2009 is missing:</p>
  
  <blockquote>
    <p>Jan-2009<br> Mar-2009<br> Apr-2009</p>
  </blockquote>
  
  <p>The day doesn't matter, just the <strong>month</strong> and <strong>year</strong> are considered.</p>
  
  <p>Is there an efficient/pretty way of doing this?</p>