title: getFullYear() is not a function
body: <p>I am developing web app by using <code>Angular</code>. When I upgrade my app to <code>Angular7</code>, Date function is not working. It gave me error such as </p>
  
  <blockquote>
    <p>DateTime.getFullYear is not a function</p>
  </blockquote>
  
  <p>It was ok before I upgraded to <code>Angular7</code>. In package.json:</p>
  
  <pre><code>"typescript": "^3.1.1", "@angular/cli": "~7.0.2",
  "@angular/complier-cli": "~7.0.0".
  </code></pre>
  
  <p>What is going on?</p>