In my point of view servers should always in the general case return a datetime in the standardized ISO 8601-format.

More info here:

• http://www.w3.org/TR/NOTE-datetime
• https://en.wikipedia.org/wiki/ISO_8601

IN this case the server would return '2011-06-29T16:52:48.000Z' which would feed directly into the JS Date object.

var utcDate = '2011-06-29T16:52:48.000Z';  // ISO-8601 formatted date returned from server
var localDate = new Date(utcDate);

The localDate will be in the right local time which in my case would be two hours later (DK time).

You really don't have to do all this parsing which just complicates stuff, as long as you are consistent with what format to expect from the server.

This is an universal solution:

function convertUTCDateToLocalDate(date) {
    var newDate = new Date(date.getTime()+date.getTimezoneOffset()*60*1000);

    var offset = date.getTimezoneOffset() / 60;
    var hours = date.getHours();

    newDate.setHours(hours - offset);

    return newDate;   
}

Usage:

var date = convertUTCDateToLocalDate(new Date(date_string_you_received));

Display the date based on the client local setting:

date.toLocaleString();

For me above solutions didn't work.

With IE the UTC date-time conversion to local is little tricky. For me, the date-time from web API is '2018-02-15T05:37:26.007' and I wanted to convert as per local timezone so I used below code in JavaScript.

var createdDateTime = new Date('2018-02-15T05:37:26.007' + 'Z');

This works for me:

function convertUTCDateToLocalDate(date) {
    return new Date(date.getTime() - date.getTimezoneOffset()*60*1000);   
}

You should get the (UTC) offset (in minutes) of the client:

var offset = new Date().getTimezoneOffset();

And then do the correspondent adding or substraction to the time you get from the server.

Hope this helps.

Put this function in your head:

<script type="text/javascript">
function localize(t)
{
  var d=new Date(t+" UTC");
  document.write(d.toString());
}
</script>

Then generate the following for each date in the body of your page:

<script type="text/javascript">localize("6/29/2011 4:52:48 PM");</script>

To remove the GMT and time zone, change the following line:

document.write(d.toString().replace(/GMT.*/g,""));

This is a simplified solution based on Adorjan Princ´s answer:

function convertUTCDateToLocalDate(date) {
    var newDate = new Date(date);
    newDate.setMinutes(date.getMinutes() - date.getTimezoneOffset());
    return newDate;
}

or simpler (though it mutates the original date):

function convertUTCDateToLocalDate(date) {
    date.setMinutes(date.getMinutes() - date.getTimezoneOffset());
    return date;
}

Usage:

var date = convertUTCDateToLocalDate(new Date(date_string_you_received));

if you have

"2021-12-28T18:00:45.959Z" format

you can use this in js :

// myDateTime is 2021-12-28T18:00:45.959Z

myDate = new Date(myDateTime).toLocaleDateString('en-US');
// myDate is 12/28/2021

myTime = new Date(myDateTime).toLocaleTimeString('en-US');
// myTime is 9:30:45 PM

you just have to put your area string instead of "en-US" (e.g. "fa-IR").

also you can use options for toLocaleTimeString like { hour: '2-digit', minute: '2-digit' }

myTime = new Date(myDateTime).toLocaleTimeString('en-US',{ hour: '2-digit', minute: '2-digit' });
// myTime is 09:30 PM

more information for toLocaleTimeString and toLocaleDateString

After trying a few others posted here without good results, this seemed to work for me:

convertUTCDateToLocalDate: function (date) {
    return new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate(),  date.getHours(), date.getMinutes(), date.getSeconds()));
}

And this works to go the opposite way, from Local Date to UTC:

convertLocalDatetoUTCDate: function(date){
    return new Date(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate(),  date.getUTCHours(), date.getUTCMinutes(), date.getUTCSeconds());
}

Add the time zone at the end, in this case 'UTC':

theDate = new Date( Date.parse('6/29/2011 4:52:48 PM UTC'));

after that, use toLocale()* function families to display the date in the correct locale

theDate.toLocaleString();  // "6/29/2011, 9:52:48 AM"
theDate.toLocaleTimeString();  // "9:52:48 AM"
theDate.toLocaleDateString();  // "6/29/2011"

Use this for UTC and Local time convert and vice versa.

//Covert datetime by GMT offset 
//If toUTC is true then return UTC time other wise return local time
function convertLocalDateToUTCDate(date, toUTC) {
    date = new Date(date);
    //Local time converted to UTC
    console.log("Time: " + date);
    var localOffset = date.getTimezoneOffset() * 60000;
    var localTime = date.getTime();
    if (toUTC) {
        date = localTime + localOffset;
    } else {
        date = localTime - localOffset;
    }
    date = new Date(date);
    console.log("Converted time: " + date);
    return date;
}

Matt's answer is missing the fact that the daylight savings time could be different between Date() and the date time it needs to convert - here is my solution:

    function ConvertUTCTimeToLocalTime(UTCDateString)
    {
        var convertdLocalTime = new Date(UTCDateString);

        var hourOffset = convertdLocalTime.getTimezoneOffset() / 60;

        convertdLocalTime.setHours( convertdLocalTime.getHours() + hourOffset ); 

        return convertdLocalTime;
    }

And the results in the debugger:

UTCDateString: "2014-02-26T00:00:00"
convertdLocalTime: Wed Feb 26 2014 00:00:00 GMT-0800 (Pacific Standard Time)

In case you don't mind usingmoment.js and your time is in UTC just use the following:

moment.utc('6/29/2011 4:52:48 PM').toDate();

if your time is not in utc but any other locale known to you, then use following:

moment('6/29/2011 4:52:48 PM', 'MM-DD-YYYY', 'fr').toDate();

if your time is already in local, then use following:

moment('6/29/2011 4:52:48 PM', 'MM-DD-YYYY');

This is what I'm doing to convert UTC to my Local Time:

const dataDate = '2020-09-15 07:08:08'
const utcDate = new Date(dataDate);
const myLocalDate = new Date(Date.UTC(
   utcDate.getFullYear(),
   utcDate.getMonth(),
   utcDate.getDate(),
   utcDate.getHours(),
   utcDate.getMinutes()
));

document.getElementById("dataDate").innerHTML = dataDate; 
document.getElementById("myLocalDate").innerHTML = myLocalDate; 

<p>UTC<p>
<p id="dataDate"></p>

<p>Local(GMT +7)<p>
<p id="myLocalDate"></p>

Result: Tue Sep 15 2020 14:08:00 GMT+0700 (Indochina Time).

To me the simplest seemed using

datetime.setUTCHours(datetime.getHours());
datetime.setUTCMinutes(datetime.getMinutes());

(i thought the first line could be enough but there are timezones which are off in fractions of hours)

Using YYYY-MM-DD hh:mm:ss format :

var date = new Date('2011-06-29T16:52:48+00:00');
date.toString() // "Wed Jun 29 2011 09:52:48 GMT-0700 (PDT)"

For converting from the YYYY-MM-DD hh:mm:ss format, make sure your date follow the ISO 8601 format.

Year: 
    YYYY (eg 1997)    
Year and month: 
    YYYY-MM (eg 1997-07)
Complete date: 
    YYYY-MM-DD (eg 1997-07-16)
Complete date plus hours and minutes:
    YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)    
Complete date plus   hours, minutes and seconds:
    YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)    
Complete date plus hours, minutes, seconds and a decimal fraction of a second
    YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00) where:

YYYY = four-digit year
MM   = two-digit month (01=January, etc.)
DD   = two-digit day of month (01 through 31)
hh   = two digits of hour (00 through 23) (am/pm NOT allowed)
mm   = two digits of minute (00 through 59)
ss   = two digits of second (00 through 59)
s    = one or more digits representing a decimal fraction of a second
TZD  = time zone designator (Z or +hh:mm or -hh:mm)

Important things to note

1. You must separate the date and the time by a T, a space will not work in some browsers
2. You must set the timezone using this format +hh:mm, using a string for a timezone (ex. : 'UTC') will not work in many browsers. +hh:mm represent the offset from the UTC timezone.

A JSON date string (serialized in C#) looks like "2015-10-13T18:58:17".

In angular, (following Hulvej) make a localdate filter:

myFilters.filter('localdate', function () {
    return function(input) {
        var date = new Date(input + '.000Z');
        return date;
    };
})

Then, display local time like:

{{order.createDate | localdate | date : 'MMM d, y h:mm a' }}

For me, this works well

if (typeof date === "number") {
  time = new Date(date).toLocaleString();
  } else if (typeof date === "string"){
  time = new Date(`${date} UTC`).toLocaleString();
}

I Answering This If Any one want function that display converted time to specific id element and apply date format string yyyy-mm-dd here date1 is string and ids is id of element that time going to display.

function convertUTCDateToLocalDate(date1, ids) 
{
  var newDate = new Date();
  var ary = date1.split(" ");
  var ary2 = ary[0].split("-");
  var ary1 = ary[1].split(":");
  var month_short = Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
  newDate.setUTCHours(parseInt(ary1[0]));
  newDate.setUTCMinutes(ary1[1]);
  newDate.setUTCSeconds(ary1[2]);
  newDate.setUTCFullYear(ary2[0]);
  newDate.setUTCMonth(ary2[1]);
  newDate.setUTCDate(ary2[2]);
  ids = document.getElementById(ids);
  ids.innerHTML = " " + newDate.getDate() + "-" + month_short[newDate.getMonth() - 1] + "-" + newDate.getFullYear() + " " + newDate.getHours() + ":" + newDate.getMinutes() + ":" + newDate.getSeconds();
            }

i know that answer has been already accepted but i get here cause of google and i did solve with getting inspiration from accepted answer so i did want to just share it if someone need.

@Adorojan's answer is almost correct. But addition of offset is not correct since offset value will be negative if browser date is ahead of GMT and vice versa. Below is the solution which I came with and is working perfectly fine for me:

// Input time in UTC
var inputInUtc = "6/29/2011 4:52:48";

var dateInUtc = new Date(Date.parse(inputInUtc+" UTC"));
//Print date in UTC time
document.write("Date in UTC : " + dateInUtc.toISOString()+"<br>");

var dateInLocalTz = convertUtcToLocalTz(dateInUtc);
//Print date in local time
document.write("Date in Local : " + dateInLocalTz.toISOString());

function convertUtcToLocalTz(dateInUtc) {
		//Convert to local timezone
		return new Date(dateInUtc.getTime() - dateInUtc.getTimezoneOffset()*60*1000);
}

This works on my side

Option 1: If date format is something like "yyyy-mm-dd" or "yyyy-mm-dd H:n:s", ex: "2021-12-16 06:07:40"

With this format It doesnt really know if its a local format or a UTC time. So since we know that the date is a UTC we have to make sure that JS will know that its a UTC. So we have to set the date as UTC.

        function setDateAsUTC(d) {
            let date = new Date(d);
            return new Date(
                Date.UTC(
                    date.getFullYear(),
                    date.getMonth(),
                    date.getDate(),
                    date.getHours(),
                    date.getMinutes(),
                    date.getSeconds()
                )
            );
        }

and then use it

let d = "2021-12-16 06:07:40";
setDateAsUTC(d).toLocaleString();

// output: 12/16/2021, 6:07:40 AM

Options 2: If UTC date format is ISO-8601. Mostly servers timestampz format are in ISO-8601 ex: '2011-06-29T16:52:48.000Z'. With this we can just pass it to the date function and toLocaleString() function.

let newDate = "2011-06-29T16:52:48.000Z"
new Date(newDate).toLocaleString();
//output: 6/29/2011, 4:52:48 PM

tl;dr (new Date('6/29/2011 4:52:48 PM UTC')).toString()

The source string must specify a time zone or UTC.

One-liner:

(new Date('6/29/2011 4:52:48 PM UTC')).toString()

Result in one of my web browsers:

"Wed Jun 29 2011 09:52:48 GMT-0700 (Pacific Daylight Time)"

This approach even selects standard/daylight time appropriately.

(new Date('1/29/2011 4:52:48 PM UTC')).toString()

Result in my browser:

"Sat Jan 29 2011 08:52:48 GMT-0800 (Pacific Standard Time)"

using dayjs library:

(new Date()).toISOString();  // returns 2021-03-26T09:58:57.156Z  (GMT time)

dayjs().format('YYYY-MM-DD HH:mm:ss,SSS');  // returns 2021-03-26 10:58:57,156  (local time)

(in nodejs, you must do before using it: const dayjs = require('dayjs'); in other environtments, read dayjs documentation.)

Based on @digitalbath answer, here is a small function to grab the UTC timestamp and display the local time in a given DOM element (using jQuery for this last part):

https://jsfiddle.net/moriz/6ktb4sv8/1/

<div id="eventTimestamp" class="timeStamp">
   </div>
   <script type="text/javascript">
   // Convert UTC timestamp to local time and display in specified DOM element
   function convertAndDisplayUTCtime(date,hour,minutes,elementID) {
    var eventDate = new Date(''+date+' '+hour+':'+minutes+':00 UTC');
    eventDate.toString();
    $('#'+elementID).html(eventDate);
   }
   convertAndDisplayUTCtime('06/03/2015',16,32,'eventTimestamp');
   </script>

You can use momentjs ,moment(date).format() will always give result in local date.

Bonus , you can format in any way you want. For eg.

moment().format('MMMM Do YYYY, h:mm:ss a'); // September 14th 2018, 12:51:03 pm
moment().format('dddd');                    // Friday
moment().format("MMM Do YY"); 

For more details you can refer Moment js website

In my case, I had to find the difference of dates in seconds. The date was a UTC date string, so I converted it to a local date object. This is what I did:

let utc1 = new Date();
let utc2 = null;
const dateForCompare = new Date(valueFromServer);
dateForCompare.setTime(dateForCompare.getTime() - dateForCompare.getTimezoneOffset() * 
 60000);
utc2 = dateForCompare;

const seconds = Math.floor(utc1 - utc2) / 1000;

this worked well for me with safari/chrome/firefox :

const localDate = new Date(`${utcDate.replace(/-/g, '/')} UTC`);

I believe this is the best solution:

  let date = new Date(objDate);
  date.setMinutes(date.getTimezoneOffset());

This will update your date by the offset appropriately since it is presented in minutes.

I wrote a nice little script that takes a UTC epoch and converts it the client system timezone and returns it in d/m/Y H:i:s (like the PHP date function) format:

getTimezoneDate = function ( e ) {

    function p(s) { return (s < 10) ? '0' + s : s; }        

    var t = new Date(0);
    t.setUTCSeconds(e);

    var d = p(t.getDate()), 
        m = p(t.getMonth()+1), 
        Y = p(t.getFullYear()),
        H = p(t.getHours()), 
        i = p(t.getMinutes()), 
        s = p(t.getSeconds());

    d =  [d, m, Y].join('/') + ' ' + [H, i, s].join(':');

    return d;

};