title: How to get a JS Date object from a UTC timestamp
body: <p>I get my UTC timestamp from the POCO libraries where the docs say:</p>
  
  <blockquote>
    <p>Returns the timestamp expressed in UTC-based time. UTC base time is midnight, October 15, 1582. Resolution is 100 nanoseconds. </p>
  </blockquote>
  
  <p>With this I could do something like</p>
  
  <pre><code>// utctime = 136288658313819610
  d = new Date(0);
  d.setUTCMilliseconds(utctime / 1000 / 10);
  // d = Date 2401-11-18T12:03:51.381Z
  </code></pre>
  
  <p>When using a current utctime, the resulting date is sometime in year 2401, which seems about right with an epoch in year 1582.</p>
  
  <p>To convert it to a correct UTC time, I would need to initialize <code>Date</code> with some negative value that represents the difference of the epochs, but I was unable to find such a value.</p>
  
  <p>I also need to convert the UTC time to local time for a useful result, but for that I would have to default initialize the <code>Date</code> object, right? Maybe this can be done with subtraction?</p>