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Convert Date to UTC with timezone

I'm migrating some data in my DB and have date as a string "date" : "2020-10-23",. I want to convert that date into a datetime object to store it in another field. I'm using luxon
let DateTime = luxon.DateTime;
// Function
function timeZoneToUTC(timezone, year, month, day, hours) {
const dateObj = `${year}-${month}-${day} ${hours}:00`;
let date = DateTime.fromFormat(dateObj, 'yyyy-M-d H:mm', {
zone: timezone
});
return date.toUTC().toString();
}
// Example
let record = {preparationTime: "18",
date : "2020-10-23"};
let dateISO = DateTime.fromISO(record.date, {zone: 'Europe/Amsterdam'});
dateISO = dateISO.minus({days: 1});
let year = dateISO.year;
let month = dateISO.month;
let day = dateISO.day;
record.newOrderTime = timeZoneToUTC('Europe/Amsterdam', year, month, day, 22);
console.log(record.newOrderTime);
<script src = "https://cdn.jsdelivr.net/npm/luxon#1.25.0/build/global/luxon.min.js" > </script>
The code above returns a wrong time, for example: 2020-10-23 will be 2020-10-22T20:00:00.000Z the day is correct however the time is not, it should be 21 instead of 20

This maybe due to Daylight savings times. (https://moment.github.io/luxon/docs/manual/zones.html#dst-weirdness)
To check whether current time is based on DST or not
https://moment.github.io/luxon/docs/class/src/datetime.js~DateTime.html#instance-get-isInDST

Match the Date time param with key value

I have two variables in the java-script like below.
const dbobj = {
"id": "123-456",
"dbtime": "2020-04-15T19:30:00.000z"
}
const userobj = {
id: "123-456",
usertime: {
year: 2020,
month: 04,
day: 11,
hour: 05,
minute: 12
}
}
With the above code I wish to check whether the date time from dbobj is getting match with userobj.usertime along with the ID as well.
I did it using the split feature of javascript.
But wish to know If any standard way available like using map or every function kind of.
Like somehow I can convert the dbobj.dbtime into epoch time and then I can match. Hope you got my point.
Thanks in advance.

Your answer is probably the getTime() method because it returns the number of milliseconds since the Unix Epoch.
Because JavaScript uses milliseconds as the unit of measurement, whereas Unix Time is in seconds you can do the following:
const dbobj = {
id: "123-456",
dbtime: "2020-04-15T19:30:00.000z"
}
const userobj = {
id: "123-456",
usertime: {
year: 2020,
month: 04,
day: 11,
hour: 05,
minute: 12
}
}
const date1 = Math.round(new Date(dbobj.dbtime).getTime() / 1000);
const date2 = Math.round(new Date(userobj.usertime.year, userobj.usertime.month - 1, userobj.usertime.day, userobj.usertime.hour, userobj.usertime.minute).getTime() / 1000);
console.log(date1 > date2);
console.log(date1 < date2);
console.log(date1 === date2);
For more info, you can reference this article - Date.prototype.getTime().

Better way to get the current date for the input type "date" as a default value? [duplicate]

I have a date with the format Sun May 11,2014. How can I convert it to 2014-05-11 using JavaScript?
function taskDate(dateMilli) {
var d = (new Date(dateMilli) + '').split(' ');
d[2] = d[2] + ',';
return [d[0], d[1], d[2], d[3]].join(' ');
}
var datemilli = Date.parse('Sun May 11,2014');
console.log(taskDate(datemilli));
The code above gives me the same date format, sun may 11,2014. How can I fix this?

Just leverage the built-in toISOString method that brings your date to the ISO 8601 format:
let yourDate = new Date()
yourDate.toISOString().split('T')[0]
Where yourDate is your date object.
Edit: #exbuddha wrote this to handle time zone in the comments:
const offset = yourDate.getTimezoneOffset()
yourDate = new Date(yourDate.getTime() - (offset*60*1000))
return yourDate.toISOString().split('T')[0]

You can do:
function formatDate(date) {
var d = new Date(date),
month = '' + (d.getMonth() + 1),
day = '' + d.getDate(),
year = d.getFullYear();
if (month.length < 2)
month = '0' + month;
if (day.length < 2)
day = '0' + day;
return [year, month, day].join('-');
}
console.log(formatDate('Sun May 11,2014'));
Usage example:
console.log(formatDate('Sun May 11,2014'));
Output:
2014-05-11
Demo on JSFiddle: http://jsfiddle.net/abdulrauf6182012/2Frm3/

I use this way to get the date in format yyyy-mm-dd :)
var todayDate = new Date().toISOString().slice(0, 10);
console.log(todayDate);

2020 ANSWER
You can use the native .toLocaleDateString() function which supports several useful params like locale (to select a format like MM/DD/YYYY or YYYY/MM/DD), timezone (to convert the date) and formats details options (eg: 1 vs 01 vs January).
Examples
const testCases = [
new Date().toLocaleDateString(), // 8/19/2020
new Date().toLocaleString(undefined, {year: 'numeric', month: '2-digit', day: '2-digit', weekday:"long", hour: '2-digit', hour12: false, minute:'2-digit', second:'2-digit'}),
new Date().toLocaleDateString('en-US', {year: 'numeric', month: '2-digit', day: '2-digit'}), // 08/19/2020 (month and day with two digits)
new Date().toLocaleDateString('en-ZA'), // 2020/08/19 (year/month/day) notice the different locale
new Date().toLocaleDateString('en-CA'), // 2020-08-19 (year-month-day) notice the different locale
new Date().toLocaleString("en-US", {timeZone: "America/New_York"}), // 8/19/2020, 9:29:51 AM. (date and time in a specific timezone)
new Date().toLocaleString("en-US", {hour: '2-digit', hour12: false, timeZone: "America/New_York"}), // 09 (just the hour)
]
for (const testData of testCases) {
console.log(testData)
}
Notice that sometimes to output a date in your specific desire format, you have to find a compatible locale with that format.
You can find the locale examples here: https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_tolocalestring_date_all
Please notice that locale just change the format, if you want to transform a specific date to a specific country or city time equivalent then you need to use the timezone param.

The simplest way to convert your date to the yyyy-mm-dd format, is to do this:
var date = new Date("Sun May 11,2014");
var dateString = new Date(date.getTime() - (date.getTimezoneOffset() * 60000 ))
.toISOString()
.split("T")[0];
How it works:
new Date("Sun May 11,2014") converts the string "Sun May 11,2014" to a date object that represents the time Sun May 11 2014 00:00:00 in a timezone based on current locale (host system settings)
new Date(date.getTime() - (date.getTimezoneOffset() * 60000 )) converts your date to a date object that corresponds with the time Sun May 11 2014 00:00:00 in UTC (standard time) by subtracting the time zone offset
.toISOString() converts the date object to an ISO 8601 string 2014-05-11T00:00:00.000Z
.split("T") splits the string to array ["2014-05-11", "00:00:00.000Z"]
[0] takes the first element of that array
Demo
var date = new Date("Sun May 11,2014");
var dateString = new Date(date.getTime() - (date.getTimezoneOffset() * 60000 ))
.toISOString()
.split("T")[0];
console.log(dateString);
Note :
The first part of the code (new Date(...)) may need to be tweaked a bit if your input format is different from that of the OP. As mikeypie
pointed out in the comments, if the date string is already in the expected output format and the local timezone is west of UTC, then new Date('2022-05-18') results in 2022-05-17. And a user's locale (eg. MM/DD/YYYY vs DD-MM-YYYY) may also impact how a date is parsed by new Date(...). So do some proper testing if you want to use this code for different input formats.

A combination of some of the answers:
var d = new Date(date);
date = [
d.getFullYear(),
('0' + (d.getMonth() + 1)).slice(-2),
('0' + d.getDate()).slice(-2)
].join('-');

format = function date2str(x, y) {
var z = {
M: x.getMonth() + 1,
d: x.getDate(),
h: x.getHours(),
m: x.getMinutes(),
s: x.getSeconds()
};
y = y.replace(/(M+|d+|h+|m+|s+)/g, function(v) {
return ((v.length > 1 ? "0" : "") + z[v.slice(-1)]).slice(-2)
});
return y.replace(/(y+)/g, function(v) {
return x.getFullYear().toString().slice(-v.length)
});
}
Result:
format(new Date('Sun May 11,2014'), 'yyyy-MM-dd')
"2014-05-11

If you don't have anything against using libraries, you could just use the Moments.js library like so:
var now = new Date();
var dateString = moment(now).format('YYYY-MM-DD');
var dateStringWithTime = moment(now).format('YYYY-MM-DD HH:mm:ss');
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>

You can use toLocaleDateString('fr-CA') on Date object
console.log(new Date('Sun May 11,2014').toLocaleDateString('fr-CA'));
Also I found out that those locales give right result from this locales list List of All Locales and Their Short Codes?
'en-CA'
'fr-CA'
'lt-LT'
'sv-FI'
'sv-SE'
var localesList = ["af-ZA",
"am-ET",
"ar-AE",
"ar-BH",
"ar-DZ",
"ar-EG",
"ar-IQ",
"ar-JO",
"ar-KW",
"ar-LB",
"ar-LY",
"ar-MA",
"arn-CL",
"ar-OM",
"ar-QA",
"ar-SA",
"ar-SY",
"ar-TN",
"ar-YE",
"as-IN",
"az-Cyrl-AZ",
"az-Latn-AZ",
"ba-RU",
"be-BY",
"bg-BG",
"bn-BD",
"bn-IN",
"bo-CN",
"br-FR",
"bs-Cyrl-BA",
"bs-Latn-BA",
"ca-ES",
"co-FR",
"cs-CZ",
"cy-GB",
"da-DK",
"de-AT",
"de-CH",
"de-DE",
"de-LI",
"de-LU",
"dsb-DE",
"dv-MV",
"el-GR",
"en-029",
"en-AU",
"en-BZ",
"en-CA",
"en-GB",
"en-IE",
"en-IN",
"en-JM",
"en-MY",
"en-NZ",
"en-PH",
"en-SG",
"en-TT",
"en-US",
"en-ZA",
"en-ZW",
"es-AR",
"es-BO",
"es-CL",
"es-CO",
"es-CR",
"es-DO",
"es-EC",
"es-ES",
"es-GT",
"es-HN",
"es-MX",
"es-NI",
"es-PA",
"es-PE",
"es-PR",
"es-PY",
"es-SV",
"es-US",
"es-UY",
"es-VE",
"et-EE",
"eu-ES",
"fa-IR",
"fi-FI",
"fil-PH",
"fo-FO",
"fr-BE",
"fr-CA",
"fr-CH",
"fr-FR",
"fr-LU",
"fr-MC",
"fy-NL",
"ga-IE",
"gd-GB",
"gl-ES",
"gsw-FR",
"gu-IN",
"ha-Latn-NG",
"he-IL",
"hi-IN",
"hr-BA",
"hr-HR",
"hsb-DE",
"hu-HU",
"hy-AM",
"id-ID",
"ig-NG",
"ii-CN",
"is-IS",
"it-CH",
"it-IT",
"iu-Cans-CA",
"iu-Latn-CA",
"ja-JP",
"ka-GE",
"kk-KZ",
"kl-GL",
"km-KH",
"kn-IN",
"kok-IN",
"ko-KR",
"ky-KG",
"lb-LU",
"lo-LA",
"lt-LT",
"lv-LV",
"mi-NZ",
"mk-MK",
"ml-IN",
"mn-MN",
"mn-Mong-CN",
"moh-CA",
"mr-IN",
"ms-BN",
"ms-MY",
"mt-MT",
"nb-NO",
"ne-NP",
"nl-BE",
"nl-NL",
"nn-NO",
"nso-ZA",
"oc-FR",
"or-IN",
"pa-IN",
"pl-PL",
"prs-AF",
"ps-AF",
"pt-BR",
"pt-PT",
"qut-GT",
"quz-BO",
"quz-EC",
"quz-PE",
"rm-CH",
"ro-RO",
"ru-RU",
"rw-RW",
"sah-RU",
"sa-IN",
"se-FI",
"se-NO",
"se-SE",
"si-LK",
"sk-SK",
"sl-SI",
"sma-NO",
"sma-SE",
"smj-NO",
"smj-SE",
"smn-FI",
"sms-FI",
"sq-AL",
"sr-Cyrl-BA",
"sr-Cyrl-CS",
"sr-Cyrl-ME",
"sr-Cyrl-RS",
"sr-Latn-BA",
"sr-Latn-CS",
"sr-Latn-ME",
"sr-Latn-RS",
"sv-FI",
"sv-SE",
"sw-KE",
"syr-SY",
"ta-IN",
"te-IN",
"tg-Cyrl-TJ",
"th-TH",
"tk-TM",
"tn-ZA",
"tr-TR",
"tt-RU",
"tzm-Latn-DZ",
"ug-CN",
"uk-UA",
"ur-PK",
"uz-Cyrl-UZ",
"uz-Latn-UZ",
"vi-VN",
"wo-SN",
"xh-ZA",
"yo-NG",
"zh-CN",
"zh-HK",
"zh-MO",
"zh-SG",
"zh-TW",
"zu-ZA"
];
localesList.forEach(lcl => {
if ("2014-05-11" === new Date('Sun May 11,2014').toLocaleDateString(lcl)) {
console.log(lcl, new Date('Sun May 11,2014').toLocaleDateString(lcl));
}
});

The 2021 solution using Intl.
The new Intl Object is now supported on all browsers.
You can choose the format by choosing a "locale" that uses the required format.
The Swedish locale uses the format "yyyy-mm-dd":
// Create a date
const date = new Date(2021, 10, 28);
// Create a formatter using the "sv-SE" locale
const dateFormatter = Intl.DateTimeFormat('sv-SE');
// Use the formatter to format the date
console.log(dateFormatter.format(date)); // "2021-11-28"
Downsides of using Intl:
You cannot "unformat" or "parse" strings using this method
You have to search for the required format (for instance on Wikipedia) and cannot use a format-string like "yyyy-mm-dd"

Simply use this:
var date = new Date('1970-01-01'); // Or your date here
console.log((date.getMonth() + 1) + '/' + date.getDate() + '/' + date.getFullYear());
Simple and sweet ;)

Shortest
.toJSON().slice(0,10);
var d = new Date('Sun May 11,2014' +' UTC'); // Parse as UTC
let str = d.toJSON().slice(0,10); // Show as UTC
console.log(str);

toISOString() assumes your date is local time and converts it to UTC. You will get an incorrect date string.
The following method should return what you need.
Date.prototype.yyyymmdd = function() {
var yyyy = this.getFullYear().toString();
var mm = (this.getMonth()+1).toString(); // getMonth() is zero-based
var dd = this.getDate().toString();
return yyyy + '-' + (mm[1]?mm:"0"+mm[0]) + '-' + (dd[1]?dd:"0"+dd[0]);
};
Source: https://blog.justin.kelly.org.au/simple-javascript-function-to-format-the-date-as-yyyy-mm-dd/

In the most of cases (no time zone handling) this is enough:
date.toISOString().substring(0,10)
Example
var date = new Date();
console.log(date.toISOString()); // 2022-07-04T07:14:08.925Z
console.log(date.toISOString().substring(0,10)); // 2022-07-04

Retrieve year, month, and day, and then put them together. Straight, simple, and accurate.
function formatDate(date) {
var year = date.getFullYear().toString();
var month = (date.getMonth() + 101).toString().substring(1);
var day = (date.getDate() + 100).toString().substring(1);
return year + "-" + month + "-" + day;
}
//Usage example:
alert(formatDate(new Date()));

new Date('Tue Nov 01 2022 22:14:53 GMT-0300').toLocaleDateString('en-CA');
new Date().toLocaleDateString('pt-br').split( '/' ).reverse( ).join( '-' );
or
new Date().toISOString().split('T')[0]
new Date('23/03/2020'.split('/').reverse().join('-')).toISOString()
new Date('23/03/2020'.split('/').reverse().join('-')).toISOString().split('T')[0]
Try this!

When ES2018 rolls around (works in chrome) you can simply regex it
(new Date())
.toISOString()
.replace(
/^(?<year>\d+)-(?<month>\d+)-(?<day>\d+)T.*$/,
'$<year>-$<month>-$<day>'
)
2020-07-14
Or if you'd like something pretty versatile with no libraries whatsoever
(new Date())
.toISOString()
.match(
/^(?<yyyy>\d\d(?<yy>\d\d))-(?<mm>0?(?<m>\d+))-(?<dd>0?(?<d>\d+))T(?<HH>0?(?<H>\d+)):(?<MM>0?(?<M>\d+)):(?<SSS>(?<SS>0?(?<S>\d+))\.\d+)(?<timezone>[A-Z][\dA-Z.-:]*)$/
)
.groups
Which results in extracting the following
{
H: "8"
HH: "08"
M: "45"
MM: "45"
S: "42"
SS: "42"
SSS: "42.855"
d: "14"
dd: "14"
m: "7"
mm: "07"
timezone: "Z"
yy: "20"
yyyy: "2020"
}
Which you can use like so with replace(..., '$<d>/$<m>/\'$<yy> # $<H>:$<MM>') as at the top instead of .match(...).groups to get
14/7/'20 # 8:45

const formatDate = d => [
d.getFullYear(),
(d.getMonth() + 1).toString().padStart(2, '0'),
d.getDate().toString().padStart(2, '0')
].join('-');
You can make use of padstart.
padStart(n, '0') ensures that a minimum of n characters are in a string and prepends it with '0's until that length is reached.
join('-') concatenates an array, adding '-' symbol between every elements.
getMonth() starts at 0 hence the +1.

To consider the timezone also, this one-liner should be good without any library:
new Date().toLocaleString("en-IN", {timeZone: "Asia/Kolkata"}).split(',')[0]

You can try this: https://www.npmjs.com/package/timesolver
npm i timesolver
Use it in your code:
const timeSolver = require('timeSolver');
const date = new Date();
const dateString = timeSolver.getString(date, "YYYY-MM-DD");
You can get the date string by using this method:
getString

I suggest using something like formatDate-js instead of trying to replicate it every time. Just use a library that supports all the major strftime actions.
new Date().format("%Y-%m-%d")

Unfortunately, JavaScript's Date object has many pitfalls. Any solution based on Date's builtin toISOString has to mess with the timezone, as discussed in some other answers to this question. The clean solution to represent an ISO-8601 date (without time) is given by Temporal.PlainDate from the Temporal proposal. As of February 2021, you have to choose the workaround that works best for you.
use Date with vanilla string concatenation
Assuming that your internal representation is based on Date, you can perform manual string concatenation. The following code avoids some of Date's pitfalls (timezone, zero-based month, missing 2-digit formatting), but there might be other issues.
function vanillaToDateOnlyIso8601() {
// month May has zero-based index 4
const date = new Date(2014, 4, 11);
const yyyy = date.getFullYear();
const mm = String(date.getMonth() + 1).padStart(2, "0"); // month is zero-based
const dd = String(date.getDate()).padStart(2, "0");
if (yyyy < 1583) {
// TODO: decide how to support dates before 1583
throw new Error(`dates before year 1583 are not supported`);
}
const formatted = `${yyyy}-${mm}-${dd}`;
console.log("vanilla", formatted);
}
use Date with helper library (e.g. formatISO from date-fns)
This is a popular approach, but you are still forced to handle a calendar date as a Date, which represents
a single moment in time in a platform-independent format
The following code should get the job done, though:
import { formatISO } from "date-fns";
function dateFnsToDateOnlyIso8601() {
// month May has zero-based index 4
const date = new Date(2014, 4, 11);
const formatted = formatISO(date, { representation: "date" });
console.log("date-fns", formatted);
}
find a library that properly represents dates and times
I wish there was a clean and battle-tested library that brings its own well-designed date–time representations. A promising candidate for the task in this question was LocalDate from #js-joda/core, but the library is less active than, say, date-fns. When playing around with some example code, I also had some issues after adding the optional #js-joda/timezone.
However, the core functionality works and looks very clean to me:
import { LocalDate, Month } from "#js-joda/core";
function jodaDateOnlyIso8601() {
const someDay = LocalDate.of(2014, Month.MAY, 11);
const formatted = someDay.toString();
console.log("joda", formatted);
}
experiment with the Temporal-proposal polyfill
This is not recommended for production, but you can import the future if you wish:
import { Temporal } from "proposal-temporal";
function temporalDateOnlyIso8601() {
// yep, month is one-based here (as of Feb 2021)
const plainDate = new Temporal.PlainDate(2014, 5, 11);
const formatted = plainDate.toString();
console.log("proposal-temporal", formatted);
}

Here is one way to do it:
var date = Date.parse('Sun May 11,2014');
function format(date) {
date = new Date(date);
var day = ('0' + date.getDate()).slice(-2);
var month = ('0' + (date.getMonth() + 1)).slice(-2);
var year = date.getFullYear();
return year + '-' + month + '-' + day;
}
console.log(format(date));

Date.js is great for this.
require("datejs")
(new Date()).toString("yyyy-MM-dd")

Simply Retrieve year, month, and day, and then put them together.
function dateFormat(date) {
const day = date.getDate();
const month = date.getMonth() + 1;
const year = date.getFullYear();
return `${year}-${month}-${day}`;
}
console.log(dateFormat(new Date()));

None of these answers quite satisfied me. I wanted a cross-platform solution that gave me the day in the local timezone without using any external libraries.
This is what I came up with:
function localDay(time) {
var minutesOffset = time.getTimezoneOffset()
var millisecondsOffset = minutesOffset*60*1000
var local = new Date(time - millisecondsOffset)
return local.toISOString().substr(0, 10)
}
That should return the day of the date, in YYYY-MM-DD format, in the timezone the date references.
So for example, localDay(new Date("2017-08-24T03:29:22.099Z")) will return "2017-08-23" even though it's already the 24th at UTC.
You'll need to polyfill Date.prototype.toISOString for it to work in Internet Explorer 8, but it should be supported everywhere else.

A few of the previous answer were OK, but they weren't very flexible. I wanted something that could really handle more edge cases, so I took #orangleliu 's answer and expanded on it. https://jsfiddle.net/8904cmLd/1/
function DateToString(inDate, formatString) {
// Written by m1m1k 2018-04-05
// Validate that we're working with a date
if(!isValidDate(inDate))
{
inDate = new Date(inDate);
}
// See the jsFiddle for extra code to be able to use DateToString('Sun May 11,2014', 'USA');
//formatString = CountryCodeToDateFormat(formatString);
var dateObject = {
M: inDate.getMonth() + 1,
d: inDate.getDate(),
D: inDate.getDate(),
h: inDate.getHours(),
m: inDate.getMinutes(),
s: inDate.getSeconds(),
y: inDate.getFullYear(),
Y: inDate.getFullYear()
};
// Build Regex Dynamically based on the list above.
// It should end up with something like this: "/([Yy]+|M+|[Dd]+|h+|m+|s+)/g"
var dateMatchRegex = joinObj(dateObject, "+|") + "+";
var regEx = new RegExp(dateMatchRegex,"g");
formatString = formatString.replace(regEx, function(formatToken) {
var datePartValue = dateObject[formatToken.slice(-1)];
var tokenLength = formatToken.length;
// A conflict exists between specifying 'd' for no zero pad -> expand
// to '10' and specifying yy for just two year digits '01' instead
// of '2001'. One expands, the other contracts.
//
// So Constrict Years but Expand All Else
if (formatToken.indexOf('y') < 0 && formatToken.indexOf('Y') < 0)
{
// Expand single digit format token 'd' to
// multi digit value '10' when needed
var tokenLength = Math.max(formatToken.length, datePartValue.toString().length);
}
var zeroPad = (datePartValue.toString().length < formatToken.length ? "0".repeat(tokenLength) : "");
return (zeroPad + datePartValue).slice(-tokenLength);
});
return formatString;
}
Example usage:
DateToString('Sun May 11,2014', 'MM/DD/yy');
DateToString('Sun May 11,2014', 'yyyy.MM.dd');
DateToString(new Date('Sun Dec 11,2014'),'yy-M-d');

If you use momentjs, now they include a constant for that format YYYY-MM-DD:
date.format(moment.HTML5_FMT.DATE)

You can use this function for better format and easy of use:
function convert(date) {
const d = Date.parse(date)
const date_obj = new Date(d)
return `${date_obj.getFullYear()}-${date_obj.toLocaleString("default", { month: "2-digit" })}-${date_obj.toLocaleString("default", { day: "2-digit"})}`
}
This function will format the month as 2-digit output as well as the days

Yet another combination of the answers. Nicely readable, but a little lengthy.
function getCurrentDayTimestamp() {
const d = new Date();
return new Date(
Date.UTC(
d.getFullYear(),
d.getMonth(),
d.getDate(),
d.getHours(),
d.getMinutes(),
d.getSeconds()
)
// `toIsoString` returns something like "2017-08-22T08:32:32.847Z"
// and we want the first part ("2017-08-22")
).toISOString().slice(0, 10);
}

How to the get the beginning of day of a date in javascript -- factoring in timezone

I am struggling to find out the beginning of day factoring in timezones in javascript. Consider the following:
var raw_time = new Date(this.created_at);
var offset_time = new Date(raw_hour.getTime() + time_zone_offset_in_ms);
// This resets timezone to server timezone
var offset_day = new Date(offset_time.setHours(0,0,0,0))
// always returns 2011-12-08 05:00:00 UTC, no matter what the offset was!
// This has the same issue:
var another_approach_offset_day = new Date(offset_time.getFullYear(),offset_time.getMonth(),offset_time.getHours())
I expect when i pass a Pacific Timezone offset, to get: 2011-12-08 08:00:00 UTC and so on.
What is the correct way to achieve this?
I think that part of the issue is that setHours method sets the hour (from 0 to 23), according to local time.
Also note that I am using javascript embedded in mongo, so I am unable to use any additional libraries.
Thanks!
Jeez, so this was really hard for me, but here is the final solution that I came up with the following solution. The trick was I need to use setHours or SetUTCHours to get the beginning of a day -- the only choices I have are system time and UTC. So I get the beginning of a UTC day, then add back the offset!
// Goal is given a time and a timezone, find the beginning of day
function(timestamp,selected_timezone_offset) {
var raw_time = new Date(timestamp)
var offset_time = new Date(raw_time.getTime() + selected_timezone_offset);
offset_time.setUTCHours(0,0,0,0);
var beginning_of_day = new Date(offset_time.getTime() - selected_timezone_offset);
return beginning_of_day;
}

In JavaScript all dates are stored as UTC. That is, the serial number returned by date.valueOf() is the number of milliseconds since 1970-01-01 00:00:00 UTC. But, when you examine a date via .toString() or .getHours(), etc., you get the value in local time. That is, the local time of the system running the script. You can get the value in UTC with methods like .toUTCString() or .getUTCHours(), etc.
So, you can't get a date in an arbitrary timezone, it's all UTC (or local). But, of course, you can get a string representation of a date in whatever timezone you like if you know the UTC offset. The easiest way would be to subtract the UTC offset from the date and call .getUTCHours() or .toUTCString() or whatever you need:
var d = new Date();
d.setMinutes(d.getMinutes() - 480); // get pacific standard time
d.toUTCString(); // returns "Fri, 9 Dec 2011 12:56:53 UTC"
Of course, you'll need to ignore that "UTC" at the end if you use .toUTCString(). You could just go:
d.toUTCString().replace(/UTC$/, "PST");
Edit: Don't worry about when timezones overlap date boundaries. If you pass setHours() a negative number, it will subtract those hours from midnight yesterday. Eg:
var d = new Date(2011, 11, 10, 15); // d represents Dec 10, 2011 at 3pm local time
d.setHours(-1); // d represents Dec 9, 2011 at 11pm local time
d.setHours(-24); // d represents Dec 8, 2011 at 12am local time
d.setHours(52); // d represents Dec 10, 2011 at 4am local time

Where does the time_zone_offset_in_ms variable you use come from? Perhaps it is unreliable, and you should be using Date's getTimezoneOffset() method. There is an example at the following URL:
http://www.w3schools.com/jsref/jsref_getTimezoneOffset.asp

If you know the date from a different date string you can do the following:
var currentDate = new Date(this.$picker.data('date'));
var today = new Date();
today.setHours(0, -currentDate.getTimezoneOffset(), 0, 0);
(based on the codebase for a project I did)

var aDate = new Date();
var startOfTheDay = new Date(aDate.getTime() - aDate.getTime() % 86400000)
Will create the beginning of the day, of the day in question

You can make use of Intl.DateTimeFormat. This is also how luxon handles timezones.
The code below can convert any date with any timezone to its beginging/end of the time.
const beginingOfDay = (options = {}) => {
const { date = new Date(), timeZone } = options;
const parts = Intl.DateTimeFormat("en-US", {
timeZone,
hourCycle: "h23",
hour: "numeric",
minute: "numeric",
second: "numeric",
}).formatToParts(date);
const hour = parseInt(parts.find((i) => i.type === "hour").value);
const minute = parseInt(parts.find((i) => i.type === "minute").value);
const second = parseInt(parts.find((i) => i.type === "second").value);
return new Date(
1000 *
Math.floor(
(date - hour * 3600000 - minute * 60000 - second * 1000) / 1000
)
);
};
const endOfDay = (...args) =>
new Date(beginingOfDay(...args).getTime() + 86399999);
const beginingOfYear = () => {};
console.log(beginingOfDay({ timeZone: "GMT" }));
console.log(endOfDay({ timeZone: "GMT" }));
console.log(beginingOfDay({ timeZone: "Asia/Tokyo" }));
console.log(endOfDay({ timeZone: "Asia/Tokyo" }));

Display date/time in user's locale format and time offset

I want the server to always serve dates in UTC in the HTML, and have JavaScript on the client site convert it to the user's local timezone.
Bonus if I can output in the user's locale date format.

Seems the most foolproof way to start with a UTC date is to create a new Date object and use the setUTC… methods to set it to the date/time you want.
Then the various toLocale…String methods will provide localized output.
Example:
// This would come from the server.
// Also, this whole block could probably be made into an mktime function.
// All very bare here for quick grasping.
d = new Date();
d.setUTCFullYear(2004);
d.setUTCMonth(1);
d.setUTCDate(29);
d.setUTCHours(2);
d.setUTCMinutes(45);
d.setUTCSeconds(26);
console.log(d); // -> Sat Feb 28 2004 23:45:26 GMT-0300 (BRT)
console.log(d.toLocaleString()); // -> Sat Feb 28 23:45:26 2004
console.log(d.toLocaleDateString()); // -> 02/28/2004
console.log(d.toLocaleTimeString()); // -> 23:45:26
Some references:
toLocaleString
toLocaleDateString
toLocaleTimeString
getTimezoneOffset

You can do it with moment.js (deprecated in 2021)
It's best to parse your date string from UTC as follows (create an ISO-8601 compatible string on the server to get consistent results across all browsers):
var m = moment("2013-02-08T09:30:26Z");
Now just use m in your application, moment.js defaults to the local timezone for display operations. There are many ways to format the date and time values or extract portions of it.
You can even format a moment object in the users locale like this:
m.format('LLL') // Returns "February 8 2013 8:30 AM" on en-us
To transform a moment.js object into a different timezone (i.e. neither the local one nor UTC), you'll need the moment.js timezone extension. That page has also some examples, it's pretty simple to use.
Note: Moment JS recommends more modern alternatives, so it is probably not a good choice for new projects.

You can use new Date().getTimezoneOffset()/60 for the timezone. There is also a toLocaleString() method for displaying a date using the user's locale.
Here's the whole list: Working with Dates

In JS there are no simple and cross platform ways to format local date time, outside of converting each property as mentioned above.
Here is a quick hack I use to get the local YYYY-MM-DD. Note that this is a hack, as the final date will not have the correct timezone anymore (so you have to ignore timezone). If I need anything else more, I use moment.js.
var d = new Date();
d = new Date(d.getTime() - d.getTimezoneOffset() * 60000)
var yyyymmdd = t.toISOString().slice(0, 10);
// 2017-05-09T08:24:26.581Z (but this is not UTC)
The d.getTimezoneOffset() returns the time zone offset in minutes, and the d.getTime() is in ms, hence the x 60,000.

2021 - you can use the browser native Intl.DateTimeFormat
const utcDate = new Date(Date.UTC(2020, 11, 20, 3, 23, 16, 738));
console.log(new Intl.DateTimeFormat().format(utcDate));
// expected output: "21/04/2021", my locale is Switzerland
Below is straight from the documentation:
const date = new Date(Date.UTC(2020, 11, 20, 3, 23, 16, 738));
// Results below assume UTC timezone - your results may vary
// Specify default date formatting for language (locale)
console.log(new Intl.DateTimeFormat('en-US').format(date));
// expected output: "12/20/2020"
// Specify default date formatting for language with a fallback language (in this case Indonesian)
console.log(new Intl.DateTimeFormat(['ban', 'id']).format(date));
// expected output: "20/12/2020"
// Specify date and time format using "style" options (i.e. full, long, medium, short)
console.log(new Intl.DateTimeFormat('en-GB', { dateStyle: 'full', timeStyle: 'long' }).format(date));
// Expected output "Sunday, 20 December 2020 at 14:23:16 GMT+11"

Once you have your date object constructed, here's a snippet for the conversion:
The function takes a UTC formatted Date object and format string.
You will need a Date.strftime prototype.
function UTCToLocalTimeString(d, format) {
if (timeOffsetInHours == null) {
timeOffsetInHours = (new Date().getTimezoneOffset()/60) * (-1);
}
d.setHours(d.getHours() + timeOffsetInHours);
return d.strftime(format);
}

// new Date(year, monthIndex [, day [, hours [, minutes [, seconds [, milliseconds]]]]])
var serverDate = new Date(2018, 5, 30, 19, 13, 15); // just any date that comes from server
var serverDateStr = serverDate.toLocaleString("en-US", {
year: 'numeric',
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
second: 'numeric'
})
var userDate = new Date(serverDateStr + " UTC");
var locale = window.navigator.userLanguage || window.navigator.language;
var clientDateStr = userDate.toLocaleString(locale, {
year: 'numeric',
month: 'numeric',
day: 'numeric'
});
var clientDateTimeStr = userDate.toLocaleString(locale, {
year: 'numeric',
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
second: 'numeric'
});
console.log("Server UTC date: " + serverDateStr);
console.log("User's local date: " + clientDateStr);
console.log("User's local date&time: " + clientDateTimeStr);

Here's what I've used in past projects:
var myDate = new Date();
var tzo = (myDate.getTimezoneOffset()/60)*(-1);
//get server date value here, the parseInvariant is from MS Ajax, you would need to do something similar on your own
myDate = new Date.parseInvariant('<%=DataCurrentDate%>', 'yyyyMMdd hh:mm:ss');
myDate.setHours(myDate.getHours() + tzo);
//here you would have to get a handle to your span / div to set. again, I'm using MS Ajax's $get
var dateSpn = $get('dataDate');
dateSpn.innerHTML = myDate.localeFormat('F');

The .getTimezoneOffset() method reports the time-zone offset in minutes, counting "westwards" from the GMT/UTC timezone, resulting in an offset value that is negative to what one is commonly accustomed to. (Example, New York time would be reported to be +240 minutes or +4 hours)
To the get a normal time-zone offset in hours, you need to use:
var timeOffsetInHours = -(new Date()).getTimezoneOffset()/60
Important detail:
Note that daylight savings time is factored into the result - so what this method gives you is really the time offset - not the actual geographic time-zone offset.

With date from PHP code I used something like this..
function getLocalDate(php_date) {
var dt = new Date(php_date);
var minutes = dt.getTimezoneOffset();
dt = new Date(dt.getTime() + minutes*60000);
return dt;
}
We can call it like this
var localdateObj = getLocalDate('2015-09-25T02:57:46');

I mix the answers so far and add to it, because I had to read all of them and investigate additionally for a while to display a date time string from db in a user's local timezone format.
The datetime string comes from a python/django db in the format: 2016-12-05T15:12:24.215Z
Reliable detection of the browser language in JavaScript doesn't seem to work in all browsers (see JavaScript for detecting browser language preference), so I get the browser language from the server.
Python/Django: send request browser language as context parameter:
language = request.META.get('HTTP_ACCEPT_LANGUAGE')
return render(request, 'cssexy/index.html', { "language": language })
HTML: write it in a hidden input:
<input type="hidden" id="browserlanguage" value={{ language }}/>
JavaScript: get value of hidden input e.g. en-GB,en-US;q=0.8,en;q=0.6/ and then take the first language in the list only via replace and regular expression
const browserlanguage = document.getElementById("browserlanguage").value;
var defaultlang = browserlanguage.replace(/(\w{2}\-\w{2}),.*/, "$1");
JavaScript: convert to datetime and format it:
var options = { hour: "2-digit", minute: "2-digit" };
var dt = (new Date(str)).toLocaleDateString(defaultlang, options);
See: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString
The result is (browser language is en-gb): 05/12/2016, 14:58

The best solution I've come across is to create [time display="llll" datetime="UTC TIME" /] Tags, and use javascript (jquery) to parse and display it relative to the user's time.
http://momentjs.com/ Moment.js
will display the time nicely.

You could use the following, which reports the timezone offset from GMT in minutes:
new Date().getTimezoneOffset();
Note :
- this function return a negative number.

getTimeZoneOffset() and toLocaleString are good for basic date work, but if you need real timezone support, look at mde's TimeZone.js.
There's a few more options discussed in the answer to this question

To convert date to local date use toLocaleDateString() method.
var date = (new Date(str)).toLocaleDateString(defaultlang, options);
To convert time to local time use toLocaleTimeString() method.
var time = (new Date(str)).toLocaleTimeString(defaultlang, options);

A very old question but perhaps this helps someone stumbling into this.
Below code formats an ISO8601 date string in a human-friendly format corresponding the user's time-zone and locale. Adapt as needed. For example: for your app, are the hours, minutes, seconds even significant to display to the user for dates more than 1 days, 1 week, 1 month, 1 year or whatever old?
Also depending on your application's implementation, don't forget to re-render periodically.
(In my code below at least every 24hours).
export const humanFriendlyDateStr = (iso8601) => {
// Examples (using Node.js):
// Get an ISO8601 date string using Date()
// > new Date()
// 2022-04-08T22:05:18.595Z
// If it was earlier today, just show the time:
// > humanFriendlyDateStr('2022-04-08T22:05:18.595Z')
// '3:05 PM'
// If it was during the past week, add the day:
// > humanFriendlyDateStr('2022-04-07T22:05:18.595Z')
// 'Thu 3:05 PM'
// If it was more than a week ago, add the date
// > humanFriendlyDateStr('2022-03-07T22:05:18.595Z')
// '3/7, 2:05 PM'
// If it was more than a year ago add the year
// > humanFriendlyDateStr('2021-03-07T22:05:18.595Z')
// '3/7/2021, 2:05 PM'
// If it's sometime in the future return the full date+time:
// > humanFriendlyDateStr('2023-03-07T22:05:18.595Z')
// '3/7/2023, 2:05 PM'
const datetime = new Date(Date.parse(iso8601))
const now = new Date()
const ageInDays = (now - datetime) / 86400000
let str
// more than 1 year old?
if (ageInDays > 365) {
str = datetime.toLocaleDateString([], {
year: 'numeric',
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
})
// more than 1 week old?
} else if (ageInDays > 7) {
str = datetime.toLocaleDateString([], {
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
})
// more than 1 day old?
} else if (ageInDays > 1) {
str = datetime.toLocaleDateString([], {
weekday: 'short',
hour: 'numeric',
minute: 'numeric',
})
// some time today?
} else if (ageInDays > 0) {
str = datetime.toLocaleTimeString([], {
timeStyle: 'short',
})
// in the future?
} else {
str = datetime.toLocaleDateString([], {
year: 'numeric',
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
})
}
return str
}
Inspired from: https://alexwlchan.net/2020/05/human-friendly-dates-in-javascript/
Tested using Node.js

Don't know how to do locale, but javascript is a client side technology.
usersLocalTime = new Date();
will have the client's time and date in it (as reported by their browser, and by extension the computer they are sitting at). It should be trivial to include the server's time in the response and do some simple math to guess-timate offset.