title: Date.getSeconds() isn't returning what I'm expecting
body: <p>I have the following code:</p>
  
  <pre><code>let startDate = new Date(someDateCreated);
  let timerDate = new Date(null);
  timerDate.setSeconds((currentTime - startDate) / 1000);
  
  console.log(timerDate.getSeconds());
  </code></pre>
  
  <p>Assuming <code>currentTime</code> is always now and <code>someDateCreated</code> starts at 2 minutes ago, I'd expect to log <code>120</code> but it is logging 1. And if I <code>setInterval</code> a function that does this every second it just counts <code>1, 2, 3...</code> Doing the following</p>
  
  <p><code>console.log((currentTime - startDate) / 1000);</code></p>
  
  <p>does what I'd expect. Why does <code>Date.getSeconds()</code> not give me the seconds I set on it?</p>
  
  <p>Here's a <a href="https://codepen.io/anon/pen/MmBgjw" rel="nofollow noreferrer">pen</a>.</p>