title: Change background DIV depending on the time of day
body: <p>All my question is in the title: How can I change my background DIV depending on the time of day?</p>
  
  <p>I tried traditional Javascript :</p>
  
  <pre><code>var d = new Date(event.starthourid),
      h = d.getHours(event.starthourid),
      i;
  
      if (h &lt; 06) i = "night.jpg";
      else if (h &lt; 11) i = "sunrise.jpg";
      else if (h &lt; 18) i = "sunny.jpg";
      else if (h &lt; 21) i = "sunset.jpg";
      else i = "night.jpg";
  
  document.getElementById("header-item").style.backgroundImage = "url("+i+")";
  </code></pre>
  
  <p>But since I encountered <code>ng-class</code> and <code>ng-style</code>, I understand I've been doing it wrong.  How can I accomplish the above the "Angular" way?</p>