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Javascript New Date Changing Hour Value

I am receiving times in the an AJAX request and am converting them using the new Date() function.
I receive 2013-06-18T12:00:15Z
However, somehow I get the following after new Date():
Tue Jun 18 2013 08:00:15 GMT-0400 (EDT)
Why is it not:
Tue Jun 18 2013 12:00
See the following demo:
http://www.w3schools.com/js/tryit.asp?filename=tryjs_date_convert

This is a time zone problem. You must be in the EDT timezone (GMT-0400). To correctly parse the date you should tell the parser in which timezone your date is correct.
For you parse your date like this :
new Date('2013-06-18 12:00:15 GMT-0400')
"GMT-0400" means GMT time minus 4 hours
Or if you don't wish to reformat your string, you can use the date.getUTC* functions to get the time as you parsed it.
The full list is available at Mozilla's documentation.

I agree with Vaim Caen's answer that this is a timezone issue, but not with parsing - the date is being parsed fine, but into your local timezone, while you're expecting it to be parsed into UTC date.
This answer shows how to convert from your current timezone to UTC - applying this to the TryIt demo gives:
var msec = Date.parse("2013-06-18T12:00:15Z");
// or: var msec = Date.parse("Tue Jun 18 2013 08:00:15 GMT-0400 (EDT)");
var d = new Date(msec);
d.setTime( d.getTime() + d.getTimezoneOffset()*60*1000 );
document.getElementById("demo").innerHTML = d;
Edit: If you all you're interested in is displaying the date (no further manipulations) then you can use:
d.toUTCString()
which will show the date in GMT (for me it actually shows "GMT" so most likely not of use!)
The alternative is to add a function to the prototype to show the date in whatever format you want and use the date.getUTC* methods.

How to convert a UTC time to local time javascript

I have a requirement to convert a UTC time local time based on user timezone
I have two parameters utc time and users timezone as a string
ie
0,1,2,3 ...12 (timezone)
0,-1,-2,-3 ...-12 (timezone)
var utc = "2014-10-18T06:14:41.512Z"
tz = 5.5(Indian Standard Time)
Expected result Sat Oct 18 2014 11:44:28 GMT+0530
I have tried moment js
moment("2014-10-18T06:14:41.512Z").zone('+05:30').format('YYYY-MM-DD HH:mm')
and the result is correct.
But when i change the timezone to other it is not showing as expected result
tried
moment("2014-10-18T06:14:41.512Z").zone('+12:00').format('YYYY-MM-DD HH:mm')
result "2014-10-18 18:14" Expected 2014-10-18 19:18
12 is NewZeland timezone. Please help me to solve this issue. Thank you

Check this
var date = new Date('2014-10-19 17:00:34 UTC');
date.toString();
var timezone = "America/New_York";
var utcDate = "2014-10-19T10:31:59.0537721Z";
var localDate = moment.utc(utcDate).tz(timezone).format()
Also check
http://www.digitoffee.com/programming/get-local-time-utc-using-moment-js/94/

To adhere to international standards, you need to format your UTC date to include the time delimiter T, and the zone designator Z.
Z is the timezone designator for the zero UTC offset aka Zulu time.
You can read more about the International Date Standard ISO8601 format specifics here.
Once you've conformed to the international standard, the cross browser friendly approach is simple:
new Date('2014-10-19T17:00:34Z');
// Sun Oct 19 2014 12:00:34 GMT-0500 (Central Daylight Time)

A time zone is not an offset. An offset is only part of a time zone. Many time zones alternate between two different offsets to account for daylight saving time. The time zone has to account for this, including the specific dates and times that daylight saving time begins and ends, as well as any history of changes that the time zone may have had.
The New Zealand case you gave is a perfect example. You said "12 is New Zealand timezone", and thus expected since New Zealand is in DST for that date that the conversion from 6:14 UTC to New Zealand local time would be 19:14. - 13 hours later.
But 12 doesn't fully represent New Zealand. It is just a 12 hour offset from UTC. There are plenty of other time zones that use the same offset in different ways. For example, the Marshal Islands use UTC+12 year round, without daylight saving time.
You should really read the timezone tag wiki - especially the section titled "Time Zone != Offset".
Instead of offsets, you should represent time zones with their full IANA identifier from the tz database. For example US Eastern Time is "America/New_York", Indian Time is "Asia/Kolkata", and New Zealand Time is "Pacific/Auckland". You can find more in the list on Wikipedia.
You can use moment-timezone to work with these in JavaScript.
moment("2014-10-18T06:14:41.512Z").tz('Pacific/Auckland').format('YYYY-MM-DD HH:mm')
// Output: "2014-10-18 19:14"
I also cover these topics in great detail in my Date and Time Fundamentals course on Pluralsight.com.

Please Check this link
http://www.digitoffee.com/programming/get-local-time-utc-using-moment-js/94/
var timezone = "UTC+5.30";
var utcDate = "2014-10-19T10:31:59.0537721Z";
var localDate = moment.utc(utcDate).tz(timezone).format()

Javascript getDay() returns wrong result

My code
var d = new Date("2014-09-01");
var days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'];
days[d.getDay()]
I expects
days[d.getDay()] returns Monday but It got Sunday
I am located in Pacific Time California zone
Do I miss something?

Dan Tao is right, here's how you can fix the missing timezone.
var d = new Date("2014-09-01");
var days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'];
d.setTime( d.getTime() + d.getTimezoneOffset()*60000 );
http://jsfiddle.net/s1bse8fm/2/
Related: How do you create a JavaScript Date object with a set timezone without using a string representation

The string you're passing to the constructor, "2014-09-01" does not indicate a time zone. On both Chrome and Firefox (based on my tests right now), this seems to be interpreted as a GMT date. When you call getDay(), the day is given in your local time zone.
So in my case, since I am in California, the date 2014-09-01, which is midnight in GMT, is actually 5pm on August 31 in PDT.

getUTCDate() Function Issue in Different Time Zones

I am facing very strange issue kindly take a look at two examples below.
My Development Environment Time Zone: GMT+0500
When i use following function:
var d = new Date("Tue Mar 18 2014 00:00:00 GMT+0500");
var n = d.getUTCDate();
n = 17 which is correct (Return the UTC day of the month of a specific, local time, date-time) and everything works perfectly in my timezone.
My Clients Time Zone: GMT+0000
var d = new Date("Tue Mar 18 2014 00:00:00 GMT+0000");
var n = d.getUTCDate();
n = 18 which is wrong
any one put some light why is that? how to resolve this issue?
any help would be appreciated.

n = 18 which is wrong
No it's not. You supplied GMT+0000, which is the same as GMT or UTC. So the result from getUTCDate is of course the date you passed in.
I think you are confused because of how you worded this:
My Development Environment Time Zone: GMT+0500
My Clients Time Zone: GMT+0000
A time zone is not a numeric offset. A time zone can have an offset, or multiple offset, and includes the history of how the offsets have changed over time. See "Time Zone != Offset" in the timezone tag wiki.
So those might be the current offsets for you and your client, but that doesn't necessarily mean that they are always going to be in the same offset. If your client is in the UK, then they are at +0000 now, but they will soon be on +0100. See here for details.

Your first date is explicitly constructed with a time zone that results in the UTC date being 17. At midnight of the 18th in the timezone 5 hours ahead of UTC (GMT), it's still the 17th in London. Your second date is constructed with the explicit UTC timezone. At the time indicated by your second date, in other words, it's 5 o'clock in the morning in the first timezone.

Convert Javascript Date object to PST time zone

I need to pick a future date from calender, suppose the date I am selecting is 10/14/2014, now what I want is to send the date with the time to server, so that at server end it always reaches as 6am time in PST timezone and the format of date should be UTC.
What I am doing is
targetDate = new Date($("#calendar").val());
targetDate = targetDate.toUTCString();
targetDate = targetDate.addHours(14);
My understanding is that PST timezone is -8:00 so I have added 14 hours to the UTC time so that time becomes 6:00am PST
The problem I am facing is that it is not letting me to add 14 hours since the object has already been converted to string.
addHours is the custom function I am having to add the hours in given time.
If I write
targetDate = new Date($("#calendar").val());
targetDate = targetDate.addHours(14);
targetDate = targetDate.toUTCString();
then it works good but in this case problem is time will always be different when the request is coming from different timezones.
Any help is appreciated.

This worked for me:
var myDate = new Date(1633071599000)
var pstDate = myDate.toLocaleString("en-US", {
timeZone: "America/Los_Angeles"
})
console.log(pstDate)
Which outputs "9/30/2021, 11:59:59 PM"

You said:
My understanding is that PST timezone is -8:00 so I have added 14 hours to the UTC time so that time becomes 6:00am PST
Uh - no. That will put you on the following day. If you wanted to stay in PST, you would subtract 8 hours from the UTC time. -8:00 means that it is 8 hours behind UTC.
However, the Pacific Time zone isn't just fixed at PST. It alternates between PST (-8) and PDT (-7) for daylight saving time. In order to determine the correct offset, you need to use a library that implements the TZDB database. Refer to this duplicate answer here.
The only way to do it without a fancy library is to actually be in the pacific time zone. JavaScript will convert UTC dates to the local time zone for display, and it will use the correct offset. But it only knows about the local time zone. If Pacific Time is not your local time zone, then you must use a library.

Suggest you look at DateJS http://code.google.com/p/datejs/ or http://www.datejs.com/. Handles PDT for you.
Here is an alternative for you:
Use: Date.UTC(year, month, day, hours, minutes, seconds, ms)
Example:
For 1 Jan 2013 6AM PST
var date = new Date(Date.UTC(2013, 0, 1, 14, 0, 0))
console.log(date.toUTCString());
Prints: "Tue, 01 Jan 2013 14:00:00 GMT"

var date = new Date();
var utcDate = new Date(date.toUTCString());
utcDate.setHours(utcDate.getHours()-8);
var usDate = new Date(utcDate);
console.log(usDate);

document.getElementById('tmp_button-48523').addEventListener('click', function() {
let d = new Date();
let localTime = d.getTime();
let localOffset = d.getTimezoneOffset() * 60000;
let utc = localTime + localOffset;
let target_offset = -7;//PST from UTC 7 hours behind right now, will need to fix for daylight
let los_angles = utc+(3600000*target_offset);
nd = new Date(los_angles);
let current_day = nd.getDay();
let hours = nd.getHours();
let mins = nd.getMinutes();
alert("los_angles time is " + nd.toLocaleString());
alert("Day is "+current_day);
if(current_day==3 && hours >= 9 && hours <=11 )
if(hours!=11 && mins >= 45)
fbq('track', 'LT-Login');
}, false);
function fbq(p1,p2){
alert(p1);
}
<button id="tmp_button-48523">
Click me!
</button>
Here is the code that created to track fb pixel on Wednesdays between 9:45am PST and 11:00am PST

Mostly comment:
I need to pick a future date from calender, suppose the date I am
selecting is 10/14/2014,
Since there isn't a 14th month, I suppose you mean 14 October, 2014. Since this is an international forum, better to use an unambiguous format.
… and the format of date should be UTC
UTC is not a format, it's a standard time.
I think you are confused. If you want say 2014-10-14T06:00:00-08:00 in UTC, then the equivalent is 2014-10-14T14:00:00Z.
You are using the toUTCString method, but it is implementation dependent, so you'll get different results in different browsers. You probably want the toISOString method, but it's ES5 and not implemented in all browsers.
You need to provide some examples of how you want times to be converted, otherwise you may as well just get the date in ISO8601 format and append "T14:00:00Z" to it.

I think the question asks how to convert UTC to PST time (as indicated on the title). I'm making assumption that the local time is in pacific time (i.e. the server or local web browser etc)
if that's the case, in order to convert UTC time to local PST just do this
// Create date object from datetime (Assume this is the UTC /GMT) time
var date = new Date('Tue, 21 Apr 2020 09:20:30 GMT');
// Covert to local PST datetime, AGAIN this only works if the server/browser is in PST
date.toString();

I believe you can simply add 14 hours before converting to UTC.
Or you can create a new Date object out of the UTC string:
var date = new Date();
date = date.addHours(14);
var dateUTC = new Date(date.toUTCString());