title: How to ensure that timestamp is UTC time at any machine
body: <pre><code>&gt; os:system_time(seconds).
  1470361698
  </code></pre>
  
  <p>This is correct UTC timestamp, but I'm not sure if it is not system-related value. Is it?</p>
  
  <p>How then I can ensure that same program ran on different machine will still operate in UTC timezone?</p>