title: Subtract days from a DateTime
body: <p>I have the following code in my C# program.</p>
  
  <pre><code>DateTime dateForButton =  DateTime.Now;  
  dateForButton = dateForButton.AddDays(-1);  // ERROR: un-representable DateTime
  </code></pre>
  
  <p>Whenever I run it, I get the following error:</p>
  
  <blockquote>
    <p><em>The added or subtracted value results in an un-representable DateTime.</em><br/>
    <em>Parameter name: value</em></p>
  </blockquote>
  
  <p>Iv'e never seen this error message before, and don't understand why I'm seeing it.  From the answers Iv'e read so far, I'm lead to believe that I can use -1 in an add operation to subtract days, but as my question shows this is not the case for what I'm attempting to do.</p>