How to format time with moment.js zone() method? - momentjs

Question

I am using moment.js v2.5, utcOffset is not available in v2.5. I only get the current user's Time.now.utc_offset //19800(UTC offset for
India) from rails backend.
Why does zone() and utcOffset() return opposite values of each other (check the snippet of code included)?
How to calculate proper time with zone() method in moment.js ?
$(document).ready(function(){
moment.suppressDeprecationWarnings = true
$('.utc span').text(moment().utcOffset());
$('.zone span').text(moment().zone());
// 19800/60 => 330
$('.india.zone span').text(moment(1519043028734).zone(330).format('HH:mm'))
$('.india.utc span').text(moment(1519043028734). utcOffset(330).format('HH:mm'))
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.20.1/moment.min.js"></script>
<p class="zone">Zone: <span></span></p>
<p class="utc">UTC: <span></span></p>
<p class="india zone">Zone:<span></span></p>
<p class="india utc">UTC:<span></span></p>

Answer 1

utcOffset:
Get the UTC offset in minutes.
Note: Unlike moment.fn.zone this function returns the real offset from UTC, not the reverse offset (as returned by Date.prototype.getTimezoneOffset).
So, basically, zone() has the same output of Date.prototype.getTimezoneOffset:
The time-zone offset is the difference, in minutes, between UTC and local time. Note that this means that the offset is positive if the local timezone is behind UTC and negative if it is ahead. For example, for time zone UTC+10:00 (Australian Eastern Standard Time, Vladivostok Time, Chamorro Standard Time), -600 will be returned.
To get proper time with zone() you can simply change sign to your offset (e.g. -330 instead of 300)
$(document).ready(function(){
moment.suppressDeprecationWarnings = true
$('.utc span').text(moment().utcOffset());
$('.zone span').text(moment().zone());
// 19800/60 => 330
$('.india.zone span').text(moment(1519043028734).zone(330*-1).format('HH:mm'))
$('.india.utc span').text(moment(1519043028734). utcOffset(330).format('HH:mm'))
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.20.1/moment.min.js"></script>
<p class="zone">Zone: <span></span></p>
<p class="utc">UTC: <span></span></p>
<p class="india zone">Zone:<span></span></p>
<p class="india utc">UTC:<span></span></p>