Why new Date set as today gives back yesterday [duplicate] - javascript

This question already has an answer here:
Why is new Date() removing a day? - Javascript [duplicate]
(1 answer)
Closed 6 years ago.
This is the first time that I get this result.
I'm using a Telerik control RadDatePicker and I'm assigning the date client-side.
The thing is that the control doesn't accept a string as date, but a Date object in javascript
So, my code to set the date in the control is
var radDateControl = $find("radDateControl");
radDateControl.set_selectedDate(new Date('2016-04-26'));
But, I realized that the new Date is returning the date as yesterday! Why?
It's 5:58pm Eastern Time (US & Canada) right now. And if I do this
alert(new Date('2016-04-26'));
I get this
Mon Apr 25 2016 20:00:00 GMT-0400 (Eastern Daylight Time)
Why and how can I get the day as of today.
Update
What I finally did it was this. Hope it can help others.
var dateAsString = "2016-04-26";
var year = dateAsString.split('-')[0];
var month = dateAsString.split('-')[1];
var day = dateAsString.split('-')[2];
var date = new Date(Date.UTC(year, month - 1, day, 0,0,0));
date.setTime(date.getTime() + date.getTimezoneOffset() * 60 * 1000);
rpdDateControl.set_selectedDate(date);

The newly created date object is totally correct. The wrong part in here or at least the part confusing you is your browser, parsing the date object into your current timezone.
If you create a new date object and save it into a variable ...
var date = new Date('2016-04-26');
... you will get what you've asked for. A Date object representing the 26/04/2016 (in UTC).
Since you use your browser to get your date objects value, the value just gets parsed through your local timezone (in your case Eastern Daylight Time). So if you want to handle the correct date which you've used to create the new date object, you may use .toUTCString().
I know, parsing timezones can be really frustrating. In order to handle different timezones, you may try out Moment or Moment Timezone. I guess moment should fit your needs, but just for the completion.

Just use Date.now() instead. I'm not sure why the string isn't working but this will work anyways.

You are asking date 26, but with timezone changes it gives you back 2 hours, why not just alert(new Date()); and let it give you its current date?, also to check it go to the server using ssh and type date, if its not the date you are you can use tzselect to modify the server to your date

Related

Jquery countdown in UTC [duplicate]

Suppose a user of your website enters a date range.
2009-1-1 to 2009-1-3
You need to send this date to a server for some processing, but the server expects all dates and times to be in UTC.
Now suppose the user is in Alaska. Since they are in a timezone quite different from UTC, the date range needs to be converted to something like this:
2009-1-1T8:00:00 to 2009-1-4T7:59:59
Using the JavaScript Date object, how would you convert the first "localized" date range into something the server will understand?
Simple and stupid
var date = new Date();
var now_utc = Date.UTC(date.getUTCFullYear(), date.getUTCMonth(),
date.getUTCDate(), date.getUTCHours(),
date.getUTCMinutes(), date.getUTCSeconds());
console.log(new Date(now_utc));
console.log(date.toISOString());
The toISOString() method returns a string in simplified extended ISO
format (ISO 8601), which is always 24 or 27 characters long
(YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ,
respectively). The timezone is always zero UTC offset, as denoted by
the suffix "Z".
Source: MDN web docs
The format you need is created with the .toISOString() method. For older browsers (ie8 and under), which don't natively support this method, the shim can be found here:
This will give you the ability to do what you need:
var isoDateString = new Date().toISOString();
console.log(isoDateString);
For Timezone work, moment.js and moment.js timezone are really invaluable tools...especially for navigating timezones between client and server javascript.
Here's my method:
var now = new Date();
var utc = new Date(now.getTime() + now.getTimezoneOffset() * 60000);
The resulting utc object isn't really a UTC date, but a local date shifted to match the UTC time (see comments). However, in practice it does the job.
Update: This answer is a quick-and-dirty way to get the UTC date when calling utc.toString(), utc.toLocaleString(), etc. Though, there are better solutions, in particular nowadays with modern browsers, and I should work on an improved answer. Basically, now.toISOString() (IE 9+) is what you want to use.
Convert to ISO without changing date/time
var now = new Date(); // Fri Feb 20 2015 19:29:31 GMT+0530 (India Standard Time)
var isoDate = new Date(now.getTime() - now.getTimezoneOffset() * 60000).toISOString();
//OUTPUT : 2015-02-20T19:29:31.238Z
Convert to ISO with change in date/time(date/time will be changed)
isoDate = new Date(now).toISOString();
//OUTPUT : 2015-02-20T13:59:31.238Z
Fiddle link
Date.prototype.toUTCArray= function(){
var D= this;
return [D.getUTCFullYear(), D.getUTCMonth(), D.getUTCDate(), D.getUTCHours(),
D.getUTCMinutes(), D.getUTCSeconds()];
}
Date.prototype.toISO= function(){
var tem, A= this.toUTCArray(), i= 0;
A[1]+= 1;
while(i++<7){
tem= A[i];
if(tem<10) A[i]= '0'+tem;
}
return A.splice(0, 3).join('-')+'T'+A.join(':');
}
Another solution to convert to UTC and keep it as a date object:
(It works by removing the ' GMT' part from the end of the formatted string, then putting it back into the Date constructor)
const now = new Date();
const now_utc = new Date(now.toUTCString().slice(0, -4));
console.log(now_utc.toString()); // ignore the timezone
I needed to do this to interface with a datetime picker library. But in general it's a bad idea to work with dates this way.
Users generally want to work with datetimes in their local time, so you either update the server side code to parse datetime strings with offsets correctly, then convert to UTC (best option) or you convert to a UTC string client-side before sending to the server (like in Will Stern's answer)
Browsers may differ, and you should also remember to not trust any info generated by the client, that being said, the below statement works for me (Google Chrome v24 on Mac OS X 10.8.2)
var utcDate = new Date(new Date().getTime());
edit: "How is this different than just new Date()?" see here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
If no arguments are provided, the constructor creates a JavaScript Date object for the current date and time according to system settings.
Note: Where Date is called as a constructor with more than one argument, the specifed arguments represent local time. If UTC is desired, use new Date(Date.UTC(...)) with the same arguments. (note: Date.UTC() returns the number of millisecond since 1970-01-01 00:00:00 UTC)
Adding the 60000 * Date.getTimezoneOffset() as previous answers have stated is incorrect. First, you must think of all Dates/Times as already being UTC with a timezone modifier for display purposes.
Again, browsers may differ, however, Date.getTime() returns the number of milliseconds since 1970-01-01 UTC/GMT. If you create a new Date using this number as I do above, it will be UTC/GMT. However, if you display it by calling .toString() it will appear to be in your local timezone because .toString() uses your local timezone, not the timezone of the Date object it is called on.
I have also found that if you call .getTimezoneOffset() on a date, it will return your local timezone, not the timezone of the date object you called it on (I can't verify this to be standard however).
In my browser, adding 60000 * Date.getTimezoneOffset() creates a DateTime that is not UTC. However when displayed within my browser (ex: .toString() ), it displays a DateTime in my local timezone that would be correct UTC time if timezone info is ignored.
My solution keeps the date the same no matter what timezone is set on the client-side. Maybe someone will find it useful.
My use case:
I'm creating a todo app, where you set date of your task. This date should remain constant no matter what timezone you're in.
Example. You want to call your friend at 8 am on June 25th.
You create this task 5 days before (June 20th) while you're in China.
Then, on the same day, you fly to New York for a few days.
Then on June 25th, while you're still in New York, you wake up at 7:30 am (which means you should receive task notification in 30 mins (even tho it's 1:30 pm already in China where you were when creating the task)
So the task is ignoring the timezone. It means 'I want to do it at 8 am in whatever timezone I'll be in'.
What I do is let's say 'I assume you're always in London Timezone - UTC'.
What it means is - when the user picks some date in her/his Timezone - I convert this date to the same date in UTC. ie. You pick 8 am in China, but I convert it to 8 am in UTC.
Then - next time you open the app - I read the date saved in UTC and convert it to the same date in your current timezone - eg. I convert 8 am in UTC to 8 am in the New York timezone.
This solution means that the date can mean something else depending on where you are when setting it and where you're reading it, but it remains constant in a way that it 'feels' like you're always in the same timezone.
Let's write some code:
First - we have 2 main functions for converting from/to UTC ignoring timezone:
export function convertLocalDateToUTCIgnoringTimezone(date: Date) {
const timestamp = Date.UTC(
date.getFullYear(),
date.getMonth(),
date.getDate(),
date.getHours(),
date.getMinutes(),
date.getSeconds(),
date.getMilliseconds(),
);
return new Date(timestamp);
}
export function convertUTCToLocalDateIgnoringTimezone(utcDate: Date) {
return new Date(
utcDate.getUTCFullYear(),
utcDate.getUTCMonth(),
utcDate.getUTCDate(),
utcDate.getUTCHours(),
utcDate.getUTCMinutes(),
utcDate.getUTCSeconds(),
utcDate.getUTCMilliseconds(),
);
}
Then, I save/read this date like:
function saveTaskDate(localDate: Date) {
// I convert your local calendar date so it looks like you've picked it being in UTC somewhere around London
const utcDate = convertLocalDateToUTCIgnoringTimezone(localDate);
api.saveTaskDate(utcDate);
}
function readTaskDate(taskUtcDate: Date) {
// I convert this UTC date to 'look in your local timezone' as if you were now in UTC somewhere around london
const localDateWithSameDayAsUTC = convertUTCToLocalDateIgnoringTimezone(taskUtcDate);
// this date will have the same calendar day as the one you've picked previously
// no matter where you were saving it and where you are now
}
var myDate = new Date(); // Set this to your date in whichever timezone.
var utcDate = myDate.toUTCString();
Are you trying to convert the date into a string like that?
I'd make a function to do that, and, though it's slightly controversial, add it to the Date prototype. If you're not comfortable with doing that, then you can put it as a standalone function, passing the date as a parameter.
Date.prototype.getISOString = function() {
var zone = '', temp = -this.getTimezoneOffset() / 60 * 100;
if (temp >= 0) zone += "+";
zone += (Math.abs(temp) < 100 ? "00" : (Math.abs(temp) < 1000 ? "0" : "")) + temp;
// "2009-6-4T14:7:32+10:00"
return this.getFullYear() // 2009
+ "-"
+ (this.getMonth() + 1) // 6
+ "-"
+ this.getDate() // 4
+ "T"
+ this.getHours() // 14
+ ":"
+ this.getMinutes() // 7
+ ":"
+ this.getSeconds() // 32
+ zone.substr(0, 3) // +10
+ ":"
+ String(temp).substr(-2) // 00
;
};
If you needed it in UTC time, just replace all the get* functions with getUTC*, eg: getUTCFullYear, getUTCMonth, getUTCHours... and then just add "+00:00" at the end instead of the user's timezone offset.
date = '2012-07-28'; stringdate = new Date(date).toISOString();
ought to work in most newer browsers. it returns 2012-07-28T00:00:00.000Z on Firefox 6.0
My recommendation when working with dates is to parse the date into individual fields from user input. You can use it as a full string, but you are playing with fire.
JavaScript can treat two equal dates in different formats differently.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse
Never do anything like:
new Date('date as text');
Once you have your date parsed into its individual fields from user input, create a date object. Once the date object is created convert it to UTC by adding the time zone offset. I can't stress how important it is to use the offset from the date object due to DST (that's another discussion however to show why).
var year = getFullYear('date as text');
var month = getMonth('date as text');
var dayOfMonth = getDate('date as text');
var date = new Date(year, month, dayOfMonth);
var offsetInMs = ((date.getTimezoneOffset() * 60) // Seconds
* 1000); // Milliseconds
var utcDate = new Date(date.getTime + offsetInMs);
Now you can pass the date to the server in UTC time. Again I would highly recommend against using any date strings. Either pass it to the server broken down to the lowest granularity you need e.g. year, month, day, minute or as a value like milliseconds from the unix epoch.
If you are dealing with dates a lot, it's worth using moment.js (http://momentjs.com). The method to convert to UTC would be:
moment(yourTime).utc()
You can use format to change your date to any format you want:
moment(yourTime).utc().format("YYYY-MM-DD")
There is offset options in moment as well but there is an additional complementary library for dealing with timezone (http://momentjs.com/timezone/). The time conversion would be as simple as this:
moment.tz(yourUTCTime, "America/New_York")
I've found the jQuery Globalization Plugin date parsing to work best. Other methods had cross-browser issues and stuff like date.js had not been updated in quite a while.
You also don't need a datePicker on the page. You can just call something similar to the example given in the docs:
$.parseDate('yy-mm-dd', '2007-01-26');
I just discovered that the 1.2.3 version of Steven Levithan's date.format.js does just what I want. It allows you to supply a format string for a JavaScript date and will convert from local time to UTC. Here's the code I'm using now:
// JavaScript dates don't like hyphens!
var rectifiedDateText = dateText.replace(/-/g, "/");
var d = new Date(rectifiedDateText);
// Using a predefined mask from date.format.js.
var convertedDate = dateFormat(d, 'isoUtcDateTime');
Using moment.js UTC method;
const moment = require('moment');
const utc = moment.utc(new Date(string));
This function works beautifully for me.
function ParseDateForSave(dateValue) {
// create a new date object
var newDate = new Date(parseInt(dateValue.substr(6)));
// return the UTC version of the date
return newDate.toISOString();
}
This method will give you : 2017-08-04T11:15:00.000+04:30 and you can ignore zone variable to simply get 2017-08-04T11:15:00.000.
function getLocalIsoDateTime(dtString) {
if(dtString == "")
return "";
var offset = new Date().getTimezoneOffset();
var localISOTime = (new Date(new Date(dtString) - offset * 60000 /*offset in milliseconds*/)).toISOString().slice(0,-1);
//Next two lines can be removed if zone isn't needed.
var absO = Math.abs(offset);
var zone = (offset < 0 ? "+" : "-") + ("00" + Math.floor(absO / 60)).slice(-2) + ":" + ("00" + (absO % 60)).slice(-2);
return localISOTime + zone;
}
If you need Date Object
Passing only date string Date assumes time to be 00:00 shifted by time zone:
new Date('2019-03-11')
Sun Mar 10 2019 18:00:00 GMT-0600 (Central Standard Time)
If you add current hours and minutes you get proper date:
new Date('2019-03-11 ' + new Date().getHours() + ':' + new Date().getMinutes())
Mon Mar 11 2019 04:36:00 GMT-0600 (Central Standard Time)
The getTimezoneOffset() method returns the time zone difference, in
minutes, from current locale (host system settings) to UTC.
Source: MDN web docs
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+02:00, -120 will be returned.
let d = new Date();
console.log(d);
d.setTime(d.getTime() + (d.getTimezoneOffset() * 60000));
console.log(d);
NOTE: This will shift the date object time to UTC±00:00 and not convert its timezone so the date object timezone will still the same but the value will be in UTC±00:00.
This is what I have done in the past:
var utcDateString = new Date(new Date().toUTCString()).toISOString();
For other people whos goal is to get it as a "Date Object" and not as a string, and you only want to display the date/time without the TZ (probably hardcoded), what you can do is:
const now = new Date();
const year = now.getUTCFullYear();
const month = now.getUTCMonth();
const day = now.getUTCDate();
const hour = now.getUTCHours();
const tomorrowUTC= new Date();
tomorrowUTC.setDate(day + 1); // +1 because my logic is to get "tomorrow"
tomorrowUTC.setYear(year);
tomorrowUTC.setMonth(month);
tomorrowUTC.Hours(hour);
// then use the tomorrowUTC for to display/format it
// tomorrowUTC is a "Date" and not a string.
You can then do stuff like:
We will delete your account at ${format(tomorrowUTC, 'EEEE do MMMM hh:mmaaa')} UTC
(format is a date-fns function, you can use other lib if you want);
This is kinda "hacky" as this is still using your local timezone, but if you just wanna display the date and not the timezone, then this works.
If your date has the timezone on it you can use date-fns-tz:
import { zonedTimeToUtc } from 'date-fns-tz';
const dateBrazil = new Date() // I'm in Brazil, you should have or get the user timezone.
const dateUtc = zonedTimeToUtc(dateBrazil, 'America/Sao_Paulo')
Looking at your question its clear that you just want to send the date range to your backend for further post processing.
I am assuming you are conforming to the standard data guidelines which expect the data to be in a particular format. For example, I use ODATA which is a RESTfull API which expects date time objects to be in the format:-
YYYY-MM-DDT00:00:00.
That can be easily achieved via the snippet posted below(Please change the format as per your requirement).
var mydate;//assuming this is my date object which I want to expose
var UTCDateStr = mydate.getUTCFullYear() + "-" + mydate.getUTCMonth() + "-" + mydate.getUTCDate() + "T00:00:00";
If on the other hand, you are in my situation wherein you have received a date from your backend, and the browser converts that to your local date. You on the other hand are interested in the UTC date then you can perform the following:-
var mydate;//assuming this is my date object which I want to expose
var UTCDate = new Date(mydate);/*create a copy of your date object. Only needed if you for some reason need the original local date*/
UTCDate.setTime(UTCDate.getTime() + UTCDate.getTimezoneOffset() * 60 * 1000);
The code snippet above basically adds/subtracts the time added/subtracted by the browser based on the timezone.
For example if I am in EST(GMT-5) and my Service returns a date time object = Wed Aug 17 2016 00:00:00 GMT-0500
my browser automatically subtracts the timezone offset(5hrs) to get my local time. So if I try to fetch the time I get Wed Aug 16 2016 19:00:00 GMT-0500. This causes a lot of problems. There are a lot of libraries out there which will definitely make this easier but I wanted to share the pure JS approach.
For more info please have a look at: http://praveenlobo.com/blog/how-to-convert-javascript-local-date-to-utc-and-utc-to-local-date/ where in I got my inspiration.
Hope this helps!
var userdate = new Date("2009-1-1T8:00:00Z");
var timezone = userdate.getTimezoneOffset();
var serverdate = new Date(userdate.setMinutes(userdate.getMinutes()+parseInt(timezone)));
This will give you the proper UTC Date and Time.
It's because the getTimezoneOffset() will give you the timezone difference in minutes.
I recommend you that not to use toISOString() because the output will be in the string Hence in future you will not able to manipulate the date
Using moment package, you can easily convert a date string of UTC to a new Date object:
const moment = require('moment');
let b = new Date(moment.utc('2014-02-20 00:00:00.000000'));
let utc = b.toUTCString();
b.getTime();
This specially helps when your server do not support timezone and you want to store UTC date always in server and get it back as a new Date object. Above code worked for my requirement of similar issue that this thread is for. Sharing here so that it can help others. I do not see exactly above solution in any answer. Thanks.
I know this question is old, but was looking at this same issue, and one option would be to send date.valueOf() to the server instead. the valueOf() function of the javascript Date sends the number of milliseconds since midnight January 1, 1970 UTC.
valueOf()
You can use the following method to convert any js date to UTC:
let date = new Date(YOUR_DATE).toISOString()
// It would give the date in format "2020-06-16T12:30:00.000Z" where Part before T is date in YYYY-MM-DD format, part after T is time in format HH:MM:SS and Z stands for UTC - Zero hour offset
By far the best way I found to get the GMT time is first get your local date time. Then convert in to GMT String. Then use the string to build new time by removing the timezone.
let dtLocal = new Date()
let dt = new Date(dtLocal.toISOString().split('Z')[0])
Note: - it will create the new datetime in GMT. But it will be local date time as timezone will be attached to it.
Extension function:
if (!Date.prototype.toUTC){
Date.prototype.toUTC = function(){
var utcOffset = new Date().getTimezoneOffset();
var utcNow = new Date().addMinutes(utcOffset);
return utcNow;
};
}
Usage:
new Date().toUTC();

moment-timezones.js, how to convert date in spesific timezone to utc, disregarding my local timezone?

my system uses timezone UTC+03:00 ,
im trying to get a date in string format, represented by NY timezone,
and convert it to a Date object in utc
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York")
.tz("Z").toDate();
doesnt work correctly
how am i even suppose to convert to utc time?
-----------edit---------------
i got it to work, using the timezone "Africa/Accra" , where UTC offset is 0, and ther is no daylight savings time:
moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York").tz("Africa/Accra")
but this solution is a bad workaround, and if the government of Accra decide to change the time laws, will stop working!
is there a way to set the utc offset to 0 in momentjs-timezones?
As Álvaro González mentioned, that Date object does not contain Time zone information.
I do the following:
new Date(moment.tz(date, currentTimezone).tz(newTimezone).format('YYYY/MM/DD HH:mm:ss'))
where date is a date object or a string (e.g. '2017-10-30 16:30:00.0000')
so, I change date from currentTimezone to newTimezone and after that new Date object will be returned
Let's change '2017-10-30 16:30:00.0000' from UTC to America/Toronto (UTC-4)
new Date(moment.tz(date, 'UTC').tz('America/Toronto').format('YYYY/MM/DD HH:mm:ss'))
And I got
Mon Oct 30 2017 12:30:00 GMT+0400
GMT+0400 is my timezone and console.log() just shows it with any
date object and it can mislead you. Please, don't look at the this
timezone.
Let's change '2017-10-30 16:30:00.0000' from Europe/Samara (UTC+4) to America/Toronto (UTC-4)
new Date(moment.tz('2017-10-30 16:30:00.0000', 'Europe/Samara').tz('America/Toronto').format('YYYY/MM/DD HH:mm:ss'))
Firstly, moment.tz undertands that date has no timezone information and associate with Europe/Samara (UTC+4)
timezone. After that computes difference between new and old
timezone (it's -8 hours in this case)
And returns result
Mon Oct 30 2017 08:30:00 GMT+0400
And answer on your question
If xsltDate is a date object or string which do not contain timezone information
dateUTC = new Date(moment.tz(xlsxDate, "America/New_York").tz("UTC").format('YYYY/MM/DD HH:mm:ss'));
If xsltDate contain timezone information (e.g.'2013-06-01T00:00:00-04:00'), then no need to tell moment.tz which timezone xlsxDate has, just mention a new timezone
dateUTC = new Date(moment.tz(xlsxDate, "UTC").format('YYYY/MM/DD HH:mm:ss'));
Short answer is that you cannot.
The .toDate() method of the Moment library returns a native Date object. Such objects do not keep memory of any specific time zone (that's one of the reasons to use Moment in the first place), they just keep track of the exact time moment represented and merely pick a time zone when formatting to string, which is either UTC or the browser's time zone (not an arbitrary one).
The long answer is that you're probably getting correct results but are printing them with a method that uses the browser's time zone.
i found a function that does what i was trying to do, it belongs to the momentjs library itself: utcOffset(n) sets the offset to n.
(i also had to explicitly write the date string format correctly, thanks VincenzoC)
this is the code i was trying to write:
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York");
const dateUTC = dateInNY.utcOffset(0).toDate();
however, the toDate function changes the timezone to my local timezone anyway, so .utcOffset(0) is redundat, and i can just use moment this way:
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York");
const dateUTC = dateInNY.toDate();
and change the Date objects date to utc time later (in my case, the JSON.stringify stuff i use later does that for me)

Javascript Date toJSON() outputting incorrect date

I am based in Australia and while new Date() give me the current date and time in Australia, for instance
Fri Aug 26 2016 09:16:16 GMT+1000 (AUS Eastern Standard Time)
, if I write new Date().toJSON()
I get 2016-08-25T23:20:08.242Z,
how can I get the same format as in yyyy-mm-ddThh:mn:ss but keeping my local day and time, ie it should be the 26 and not the 25th.
Edit: when I write programmatically new Date(2016, 11, x) with var x = 31, using toJSON() I have no guarantee to see displayed 2016-12-31 because of timezones, so was wondering is there is a different javascript function that would give me the intended result.
I would use moment.js for that.
var date = moment("Fri Aug 26 2016 09:16:16 GMT+1000");
console.log(moment(date).format('YYYY-MM-DD T hh:mm:ss'));
https://jsfiddle.net/Refatrafi/ys4nu8o9/
toJSON() returns timestamps in ISO 8601 format. Z at the end of string means that used UTC. Date objects in ECMAScript are internally UTC. The specification for Date.prototype.toJSON says that it uses Date.prototype.toISOString, which states that "the timezone is always UTC".
The date isn't wrong, it's in UTC. Without timezone information, yyyy-mm-ddThh:mn:ss is meaningless unless you explicitly want to assume that it's in the AEST timezone.
If you're transmitting the date as a string to be parsed back into some sort of Date-like object later on (by your webserver, for example), there's nothing you need to do. 2016-08-25T23:20:08.242Z unambiguously refers to the same point in time no matter what you use to parse it.
If you're trying to format the date object and display it somewhere, you can extract the different parts of the Date object and build up the representation you want:
function format_date(d) {
var pretty_date = [d.getFullYear(), d.getMonth() + 1, d.getDate()].join('-');
var pretty_time = [d.getHours(), d.getMinutes(), d.getSeconds()].join(':');
return pretty_date + 'T' + pretty_time;
}
As the other answers have pointed out, if you plan on working more with dates, consider using a library that makes it easier. JavaScript doesn't have a very rich API, so you'll have to write more code.

How to calculate midnight for the local day from UTC time [duplicate]

This question already has answers here:
What is the best way to initialize a JavaScript Date to midnight?
(10 answers)
Closed 8 years ago.
I am using Javascript for Parse.com Cloud Code.
According to Parse.com they return UTC time. I am in EDT (GMT -4)
I'm trying to get today's date at midnight to no avail.
Here is my code:
var date = new Date();
var startDay = Math.floor((date.setUTCHours(4,0,0,0) / 1000));
So before 8pm on each day, the code returns today's date at midnight which is what I want. However, after 8pm it returns tomorrow's date at midnight. I believe the reason is due to the UTC date changing to Today+1 at midnight. But I cant figure out how to resolve this issue in a way that I get my local date at midgnight.
PS:
I also tried setHours(4,0,0,0) in vain.
If I use setUTCHours(0,0,0,0) it returns today's date at 8pm
Thank you for your help.
It's doing everything correct.
Think about it from UTC's point of view. setUTCHours(0,0,0,0) will always set it to midnight that day.
From your point of view though (GMT-4), setting the date to midnight (UTC) at 8pm (GMT-4) appears to go a day forward.
This is because when you call date.setUTCHours(), it first converts that time to UTC, then sets the hours. If you create the date on May 18th, 8pm GMT-4, then call setUTCHours(), it will first convert that date to May 19th, 12am UTC. Then it will perform the hour change.
Here's what you can do to make sure it returns midnight on the same day as the user's timezone:
const date = new Date();
// Convert to midnight in your timezone first
date.setHours(0,0,0,0);
// Convert to midnight UTC
date.setUTCHours(0,0,0,0);

How to update the date to the current date for UTC -8

I want to display a UTC date using this JavaScriptcode on my webpage.
<script>
function myDate()
{
var now = new Date();
var d = new Date(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate());
var x = document.getElementById("demo");
x.innerHTML=d;
}
</script>
With this code I am getting UTC date displayed as a local string as follows: "Thu Jul 04 2013 00:00:00 GMT+0530 (India Standard Time)"
I do not want display the string with a local time offset (GMT+0530 (IST)), instead I want the time to appear as UTC string format
The date returned by different browser are of different format
to remove GMT OFFSET from date you can use replace
var d = new Date(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate());
d = d.toString().replace(/GMT.+/,"");
Firstly, the problem is that you are instantiating a local Date object by passing in the UTC year, month and day. This then creates a local Date with the values provided. by doing this you might be creating an incorrect date based on whether you want it to be UTC or local. IN your case, if you want var now as UTC, the way you are currently instantiating is incorrect as its in local time.
Anyway, dates can be tricky in in JavaScript, so I would consider using Moment.js for this
It's a fantastic library that provides all of the functions for manipulating and converting JavaScript dates that you could ever need.
For example with moment you can just do the following:
var now = moment(); // current date and time in local format
var nowAsUTC = now.utc(); // current local date and time converted to UTC
var alsoNowAsUTC = moment.utc() // same as the line above, but staring in UTC
console.log(nowUTC.format("DD/MM/YYYY, hh:mm:ss"))// prints a pretty UTC string
Hmmm.. Are you sure you want to display UTC-8? I will take a guess that you are really wanting to convert the time to US Pacific time zone. That is not always UTC-8. Sometimes it is UTC-8, and sometimes it is UTC-7.
If you're not actually in the US Pacific Time zone, the only way to do this reliably in JavaScript is with a library that implements the TZDB database. I list several of them here.
For example, using walltime-js library, you can do the following:
var date = new Date();
var pacific = WallTime.UTCToWallTime(date, "America/Los_Angeles");
var s = pacific.toDateString() + ' ' + pacific.toFormattedTime();
// output: "Fri Apr 26 2013 5:44 PM"
You can't just add or subtract a fixed number, because the target time zone may use a different offset depending on exactly what date you're talking about. This is primarily due to Daylight Saving Time, but also because time zones have changed over time.

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