title: using DateTime object inside enum
body: <p>I have this enum:</p>
  
  <pre><code>public enum TimePeriod
  {
      Day = DateTime.Now.AddDays(-1),
      Week = DateTime.Now.AddDays(-7),
      Month = DateTime.Now.AddMonths(-1),
      AllTime = DateTime.Now
  }
  </code></pre>
  
  <p>but cant do</p>
  
  <pre><code>(DateTime)timePeriod
  </code></pre>
  
  <p>how can i get the date given an enum?</p>