title: Convert utc timestamp to local time using offset In seconds
body: <p>I need to convert utc timestamp to local time using utc offset in seconds. i had used moment-timezone library. This is my code</p>
  
  <pre><code>var moment = require('moment-timezone');
  
  var timestamp = Date.now();
  
  var IST1 = moment(timestamp).utcOffset('+05:30').format('ddd MMM D Y hh:mm:ss A ')
  console.log("IST1 '+05:30' --&gt; ", IST1);
  
  var IST2 = moment(timestamp).utcOffset('+19800').format('ddd MMM D Y hh:mm:ss A ')
  console.log("IST2 '+19800' --&gt; ", IST2);
  </code></pre>
  
  <p>But i got output like this</p>
  
  <pre><code>IST1 '+05:30' --&gt;  Mon Jun 19 2017 01:39:23 PM 
  IST2 '+19800' --&gt;  Tue Jun 20 2017 04:29:23 AM
  </code></pre>
  
  <p>Using '+05:30', i got correct time. But using '+19800' , i got wrong time. What is the actual issue related with this code?</p>