title: Daylight saving and DateTime.AddHour()
body: <p>I have an issue with the infamous daylight saving time.</p>
  
  <p>I have a list of data points, one for each hour in a year. To check if all datapoints are present, I create a time iterator like this:</p>
  
  <pre><code>DateTime timeIterator = new DateTime(year, 1, 1, 0, 0, 0);
  </code></pre>
  
  <p>iterate it with</p>
  
  <pre><code>timeIterator = timeIterator.AddHours(1);
  </code></pre>
  
  <p>and check for each iteration if the point in time is present in the list.</p>
  
  <p>The problem arises when it comes to daylight saving time. Im my example of year 2014, the clock is moved at the 30. of march from 0200 to 0300. So, after 0159 comes 0300. But DateTime.AddHours() completely ignores daylight saving. If timeIterator is at {30.03.2014 01:00:00} and I call AddHours(1) I get {30.03.2014 02:00:00} which obviously doesn't exist. </p>
  
  <p>If I now test the list against this datapoint, it is (naturaly) not in the list and I throw a wrong "missing datapoint error".</p>
  
  <p>How can I check, if my DateTime is a valid point in time?</p>
  
  <p>Thanks in advance,<br>
  Frank</p>