title: C# Adding years and days in a single DateTime variable
body: <p>Am I missing something simple?
  I am trying to calculate a date 17 years and 364 days before the given date.</p>
  
  <p>Is there a way to do this without converting everything into days?  I am trying to avoid dealing with leap years.  I am doing the following:</p>
  
  <pre><code>DateTime date = Convert.ToDateTime(tId2);
  string tId4a = Convert.ToString(tId4);
  var age1 = tId4a.Substring(0, 2);
  int age2 = Convert.ToInt32(age1) - 1;
  DateTime sub1 = date.AddYears(-age2);
  </code></pre>
  
  <p>I was hoping to do something simple like:</p>
  
  <pre><code>DateTime sub1 = date.AddYears(-age2) + date.AddDays(-364);
  </code></pre>
  
  <p>I am being told that I cannot use the '+' in the DateTime.</p>
  
  <p>Sorry, but I am new to this.  The reason the age2 variable is used is because at times that value will change.  But, the 364 should be consistent.  I am creating something to test a date boundary.</p>
  
  <p>Did I overlook something simple?</p>
  
  <p>Thanks.</p>