title: Typescript Reflect.getMetadata('design:type'..) returns Object instead of Date if the Angular 2 Stack is used
body: <p>The following code Sample is working as expected and prints out "[Function: Date]"</p>
  
  <pre><code>import 'reflect-metadata'
  function logType(target : any, key : string) {
       var t = Reflect.getMetadata("design:type", target, key);
       console.log(`${key} type: ${t.name}`);
     }
  export class Demo {
    @logType // apply property decorator
    test: Date;
  }
  let demo = new Demo();
  console.log(Reflect.getMetadata('design:type', demo, "test"));
  </code></pre>
  
  <p>If I place the same code within an Angular 2 Project, "function Object() { [native code] }" is returned.</p>
  
  <p>I prepared a Plunker for this:
  <a href="https://plnkr.co/edit/DhXT89U0q5fCOWlCrx6w?p=preview" rel="nofollow noreferrer">https://plnkr.co/edit/DhXT89U0q5fCOWlCrx6w?p=preview</a></p>
  
  <p>Reflect.getMetadata('design:type' ...) is still working for custom classes and other builtin classes. I could only produce this problem with Date.</p>
  
  <p>What am I doing wrong?</p>