This works for me:

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

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

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();
}

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).

@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);
}

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

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.

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.)

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

I've created one function which converts all the timezones into local time.

I did not used getTimezoneOffset(), because it does not returns proper offset value

Requirements:

1. npm i moment-timezone

function utcToLocal(utcdateTime, tz) {
    var zone = moment.tz(tz).format("Z") // Actual zone value e:g +5:30
    var zoneValue = zone.replace(/[^0-9: ]/g, "") // Zone value without + - chars
    var operator = zone && zone.split("") && zone.split("")[0] === "-" ? "-" : "+" // operator for addition subtraction
    var localDateTime
    var hours = zoneValue.split(":")[0]
    var minutes = zoneValue.split(":")[1]
    if (operator === "-") {
        localDateTime = moment(utcdateTime).subtract(hours, "hours").subtract(minutes, "minutes").format("YYYY-MM-DD HH:mm:ss")
    } else if (operator) {
        localDateTime = moment(utcdateTime).add(hours, "hours").add(minutes, "minutes").format("YYYY-MM-DD HH:mm:ss")
    } else {
        localDateTime = "Invalid Timezone Operator"
    }
    return localDateTime
}

utcToLocal("2019-11-14 07:15:37", "Asia/Kolkata")

//Returns "2019-11-14 12:45:37"

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;

UTC to local to ISO - Using Molp Burnbright answer

because server only accepts ISO date-time so I converted UTC to my local timezone and sent it to server in ISO format

declare this somewhere

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

and do this where you need local datetime in ISO format convertUTCDateToLocalDate(date).toISOString()

I had a similar problem, I used following code code (JavaScript) to convert UTC to local time

let a = new Date()
a = a.getFullYear().toString() + "-" + (a.getMonth() + 1).toString().padStart(2, "0") + "-" + a.getDate().toString().padStart(2, "0")
console.log(a)

You can get it done using moment.js file.

Its simple you have just mention the place of the timezone.

Example: If you to convert your datetime to Asia/Kolkata timezone,you have to just mention the name of the timezone place obtained from moment.js

var UTCDateTime="Your date obtained from UTC";
var ISTleadTime=(moment.tz(UTCDateTime, "Africa/Abidjan")).tz("Asia/Kolkata").format('YYYY-MM-DD LT');

For the TypeScript users, here is a helper function:

// Typescript Type: Date Options
interface DateOptions {
  day: 'numeric' | 'short' | 'long',
  month: 'numeric',
  year: 'numeric',
  timeZone: 'UTC',
};

// Helper Function: Convert UTC Date To Local Date
export const convertUTCDateToLocalDate = (date: Date) => {
  // Date Options
  const dateOptions: DateOptions = {
    day: 'numeric',
    month: 'numeric',
    year: 'numeric',
    timeZone: 'UTC',
  };

  // Formatted Date (4/20/2020)
  const formattedDate = new Date(date.getTime() - date.getTimezoneOffset() * 60 * 1000).toLocaleString('en-US', dateOptions);
  return formattedDate;
};