title: How to start some Method every 20 days (Windows Phone)
body: <p>In my Windows Phone Applicarion I need to implement logic to start some Method every 20 days, how can I implement this?</p>
  
  <pre><code>public void Method()
  {
  //some logic
  
  }
  </code></pre>
  
  <p><strong>Update</strong>
  For example I can fix the first start of some method, then every start of application I will fix the current date time and them calculate the differens, and if the difference between the last and first sstart of some method will be more than 30 days I will start Method(). So how can I calculate the difference (days)?</p>