javascript toISOString() ignores timezone offset

I am trying to convert Twitter datetime to a local iso-string (for prettyDate) now for 2 days. I'm just not getting the local time right..

im using the following function:

function getLocalISOTime(twDate) {
    var d = new Date(twDate);
    var utcd = Date.UTC(d.getFullYear(), d.getMonth(), d.getDate(), d.getHours(),
        d.getMinutes(), d.getSeconds(), d.getMilliseconds());

    // obtain local UTC offset and convert to msec
    localOffset = d.getTimezoneOffset() * 60000;
    var newdate = new Date(utcd + localOffset);
    return newdate.toISOString().replace(".000", "");
}

in newdate everything is ok but the toISOString() throws it back to the original time again... Can anybody help me get the local time in iso from the Twitterdate formatted as: Thu, 31 May 2012 08:33:41 +0000

moment.js is great but sometimes you don't want to pull a large number of dependencies for simple things.

The following works as well:

    var tzoffset = (new Date()).getTimezoneOffset() * 60000; //offset in milliseconds
    var localISOTime = (new Date(Date.now() - tzoffset)).toISOString().slice(0, -1);
    
    console.log(localISOTime)  // => '2015-01-26T06:40:36.181'

The slice(0, -1) gets rid of the trailing Z which represents Zulu timezone and can be replaced by your own.

My solution without using moment is to convert it to a timestamp, add the timezone offset, then convert back to a date object, and then run the toISOString()

var date = new Date(); // Or the date you'd like converted.
var isoDateTime = new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString();

moment.js FTW!!!

Just convert your date to a moment and manipulate it however you please:

var d = new Date(twDate);
var m = moment(d).format();
console.log(m);
// example output:
// 2016-01-08T00:00:00-06:00

http://momentjs.com/docs/

This date function below achieves the desired effect without an additional script library. Basically it's just a simple date component concatenation in the right format, and augmenting of the Date object's prototype.

 Date.prototype.dateToISO8601String  = function() {
	var padDigits = function padDigits(number, digits) {
		return Array(Math.max(digits - String(number).length + 1, 0)).join(0) + number;
	}
	var offsetMinutes = this.getTimezoneOffset();
	var offsetHours = offsetMinutes / 60;
	var offset= "Z";	
	if (offsetHours < 0)
	  offset = "-" + padDigits(offsetHours.replace("-","") + "00",4);
	else if (offsetHours > 0) 
	  offset = "+" + padDigits(offsetHours  + "00", 4);

	return this.getFullYear() 
			+ "-" + padDigits((this.getUTCMonth()+1),2) 
			+ "-" + padDigits(this.getUTCDate(),2) 
			+ "T" 
			+ padDigits(this.getUTCHours(),2)
			+ ":" + padDigits(this.getUTCMinutes(),2)
			+ ":" + padDigits(this.getUTCSeconds(),2)
			+ "." + padDigits(this.getUTCMilliseconds(),2)
			+ offset;
			
}

Date.dateFromISO8601 = function(isoDateString) {
	  var parts = isoDateString.match(/\d+/g);
	  var isoTime = Date.UTC(parts[0], parts[1] - 1, parts[2], parts[3], parts[4], parts[5]);
	  var isoDate = new Date(isoTime);
	  return isoDate;		
}

function test() {
	var dIn = new Date();
	var isoDateString = dIn.dateToISO8601String();
	var dOut = Date.dateFromISO8601(isoDateString);
	var dInStr = dIn.toUTCString();
	var dOutStr = dOut.toUTCString();
	console.log("Dates are equal: " + (dInStr == dOutStr));
}

Usage:

var d = new Date();
console.log(d.dateToISO8601String());

Hopefully this helps someone else.

EDIT

Corrected UTC issue mentioned in comments, and credit to Alex for the dateFromISO8601 function.

It will be very helpful to get current date and time.

var date=new Date();
  var today=new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString().replace(/T/, ' ').replace(/\..+/, '');  

Using moment.js, you can use keepOffset parameter of toISOString:

toISOString(keepOffset?: boolean): string;

moment().toISOString(true)

Moment js solution to this is

var d = new Date(new Date().setHours(0,0,0,0));
m.add(m.utcOffset(), 'm')
m.toDate().toISOString()
// output "2019-07-18T00:00:00.000Z"