title: return difference between now and a given date with conditions
body: <p>I'm trying a very simple idea but hard to implement one.</p>
  <p>I want to return the difference between two given dates and times in seconds. Note I want to get the same result in these conditions:</p>
  <ul>
  <li>No matter if we test it in Chrome or Firefox. it should return the same result in both.</li>
  <li>No matter if the end-user sets the Time Zone in his/her system in different time zones.</li>
  </ul>
  <p>So I tried this:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>// input your custom Date below
  const date = new Date('2020-6-24 14:22:00'); // Set End Time 
  const dif = (date.getTime() / 1000) - ((new Date().getTime())/1000);
  console.log(dif);</code></pre>
  </div>
  </div>
  </p>
  <p>if you check this with <strong>different browsers</strong> with <strong>different timezones</strong> set in your system you will get different results!</p>
  <p>I want all users (Those who set the timezone to Havana and Those who set the time zone to Tehran on their systems) see the same result.</p>
  <p>The same result is the only thing I can think of right now.</p>
  <p>The wired and confusing thing here is that if I log this simple log, I have different results in Firefox and Chrome:</p>
  <pre><code>console.log(new Date());
  </code></pre>
  <p>Note: I set my system's timezone to Havana.</p>