I need to take an hour and convert it to local time as such :
const dataDate = '07:08'
const utcDate = new Date(dataDate);
console.log(utcDate)
there are a few problems with my approach
this only works if i add a date too
this converts to utc
I need to only convert the hour to local time, I also need to parse it to something like this :
[parseInt(hour), 0, 0, 0].map(function (x) { return parseInt(x, 10); })
To give more context, I need to create a shareable calendar with a specific schedule, and the user can set the specific hours for some event to be displayed.
If you have access to the full date
Considering your use-case is that of a shareable calendar, I'm assuming you
have access to the full UTC date. If that's not the case, skip to the next
section.
// The important thing is getting a `Date` object. The timezone in the timestamp
// doesn't really matter at this point. It will be handled internally anyway.
const date = new Date("2011-11-11T07:08:00Z");
Once you have the date object, if all you really want to get is the hour,
you can do so with the methods below. But note that you should probably use the same method for getting not only the hours, but any part of the date or time throughout your application.
const utcHour = date.getUTCHours(); //> 7
// For the hour according to the timezone configured in the RUNTIME
// environment (e.g. the user's browser, if running on the client side):
const runtimeHour = date.getHours(); //> 8 (depends on the runtime timezone)
// For an arbitrary timezone, in case you have the user's timezone stored in
// a config you could use the `.toLocaleTimeString()` method.
// Note that this method is VERY slow (~6000 times slower than `.getHours()`
// for example in a quick benchmark I ran in my machine on Node 16). You
// should probably be careful about how often this is being called (e.g. in
// loops or in a frontend component that is frequently updated/rendered).
const tzHour = Number(date.toLocaleTimeString("en", {
hour: "numeric", // omit minutes and seconds
hour12: false, // force it to be 0-23
timeZone: "America/Sao_Paulo" // set the user's timezone
})); //> 5
Which one you should use really depends on your exact implementation. You might also want to check this answer that further explains how time zones are handled by Date.
NOTE: the .toLocaleTimeString() method depends on the
Intl.DateTimeFormat API. Check Date.prototype.toLocaleTimeString() at MDN
for a compatibility table.
Note about manually calculating time offsets
You need the date in order to reliably adjust the time.
If you don't have the date for some reason, you could do so but that would
mean quite some work and it would never really be reliable, as you would not be
able to factor in Daylight Saving Time adjustments, for example.
Also keep in mind that some timezones operate on fractions of an hour:
+XX30: Asia/Tehran, Asia/Kabul, Australia/Adelaide...
+XX45: Australia/Eucla
Australia/Lord_Howe has a Daylight Saving Time adjustment of 30 mins;
Depending on the requirements of your application, calculating this manually
might not be as simple as you expect. I would recommend to delegate these
calculations to the internal Date implementation (as shown in the previous section) instead of trying to adjust the time manually (keep in mind you would have to handle overflows from min → hour → day → month → year).
About parsing the time string
As for the parsing of the time string, you mentioned in your question, you could do something like:
const rawTime = "07:08";
const [hour, minutes, seconds = 0] = rawTime.split(":").map(Number); //> [7, 8, 0]
// or if you only care about the hours
const hour = Number(rawTime.split(":", 1)); //> 7
// or you could also use a quirk of `parseInt()`, as it ignores everything
// starting at the first non-numeric character:
const hour = parseInt(rawTime); //> 7
If you instantiate a new date with new Date() the retuned value is current date/time in UTC timezone.
You can then set a specific hour/minute to that using Date.setHours() and Date.setMinutes().
Finally you can convert that UTC date to local date via Date.toLocaleDateString()
So I would do something like this for your case:
const date = new Date();
const [hour, minute] = '7:28'.split(':')
const options = {
year: 'numeric',
month: 'long',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
second: 'numeric',
};
date.setHours(hour);
date.setMinutes(minute);
console.log(date.toLocaleDateString('en-US', options));
Related
I am using Javascript code such as that shown below, and recently found that while Date.prototype.toLocaleTimeString() on one machine appends " GMT" or " BST" (depending on the time of year); on another machine, nothing is appended.
var m = new Date();
var time = m.toLocaleTimeString();
I use the returned string to create a log file, and would like the file names to have a canonical structure. I don't mind which of the two string formats is returned, as long as it is the same on both machines.
By the way, I also tried providing first and second arguments, such as m.toLocaleTimeString('en-gb', { hour: '2-digit', minute: '2-digit', second: '2-digit' }), or m.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit', second: '2-digit' }), but then the seconds are no longer included in the returned string.
You could create a custom format function for your logs, using the Date.getHours(), getMinutes() etc.
This should be consistent across platforms and would allow any customization to be added easily.
function formatTimestamp(date) {
const hms = [date.getHours(), date.getMinutes(), date.getSeconds()];
return hms.map(s => (s + '').padStart(2, '0')).join(':');
}
console.log('Timestamp:', formatTimestamp(new Date()));
The behavior you are seeing with the toLocaleTimeString() method is likely due to differences in the default time zone settings on the two machines. The method returns a string that represents the time in the current time zone, which can be different depending on the machine's settings.
You can use toUTCString() method to get a string representation of the date in UTC format, this will always return the same format, regardless of the machine's time zone settings.
var m = new Date();
var time = m.toUTCString();
Another approach, you can use moment.js library, this library will handle timezone and other time related issues, and it's very useful when you are working with dates and time, it will give you a consistent format across different environments.
var moment = require('moment');
var time = moment().format('HH:mm:ss');
The moment().format('HH:mm:ss') will give you the time in the format of HH:mm:ss and you can use this as your log file name.
Additionally, you can also set your machine's time zone to a specific value using the Intl.DateTimeFormat() method, this will help you to get the same format across different machines.
var m = new Date();
var options = {timeZone: 'UTC', hour: '2-digit', minute: '2-digit', second: '2-digit'};
var time = new Intl.DateTimeFormat('en-GB', options).format(m);
This will give you the time formatted to 'en-GB' time zone and with the hour, minute and second digits.
I am using Mongoose and Luxon to display a date, selected by the user from a form. But the date is console.logging one date, but displaying on the page as the day before.
This is my model:
const mongoose = require("mongoose");
const { DateTime, Settings } = require("luxon");
// Configure time zone
console.log(Settings);
const Schema = mongoose.Schema;
let AccomplishmentSchema = new Schema({
dateInput: {
type: Date,
required: true,
},
textInput: {
type: String,
required: true,
},
});
AccomplishmentSchema.virtual("dateInput_formatted").get(function () {
return DateTime.fromJSDate(this.dateInput).toLocaleString(DateTime.DATE_FULL); // format 'YYYY-MM-DD
});
module.exports = mongoose.model("Accomplishment", AccomplishmentSchema);
And this is my console log vs what is showing up on the page
dateInput: 2023-01-01T00:00:00.000Z,
textInput: 'etst',
December 31, 2022
etst
I can only assume this has to do with some kind of time conversion, but I've tried changing the time zone, and the settings, although I could've read the docs wrong. I cannot find a way to fix this issue.
When working with JS Date, the most important thing to understand is that Date doesn't store or know about a time zone. It simply stores the number of milliseconds since midnight on Jan 1, 1970 (aka UNIX epoch) in the UTC time zone. Then, when you call Date methods, the results are calculated for the current user's time zone (for methods like getMinutes()) or UTC (for methods like getUTCMinutes()). But the underlying data inside the Date is just a timezone-less number of milliseconds.
With that in mind, let's look at a simple example: new Date(0), which is equivalent to new Date('1970-01-01T00:00Z').
If your computer's time zone set to the Europe/Paris time zone, then when you call new Date(0).toLocaleDateString('en-US') then you'll get a result of '1/1/1970'. But if you change your computer's time zone to America/Los_Angeles and run the same code, you'll get a result of '12/31/1969'.
This happens because the Date's stored value corresponds to midnight on Jan 1, 1970 in the UTC time zone. In Paris that instant was 1:00AM on Jan 1, 1970, while in California it was 4:00PM on December 31, 1969. The same exact Date will print a different date depending on the time zone that's active at the time that date is printed.
Where this becomes particularly problematic is in cases where you're trying to express a date without a time. For example, assume you store a Date value of 2023-01-01T00:00:00.000Z in MongoDB.
When you display that Date in a date picker in a browser in California, the date shown will be Dec 31, 2022, because California is 8 hours ahead of UTC.
One way to solve this problem is to tell Date that the date you're using is a UTC date. Like this:
utcDateStoredInMongoDB = new Date ('2023-01-01T00:00:00.000Z');
// Get the year, month, and day in that Date, from the perspective
// of the UTC time zone.
year = utcDateStoredInMongoDB.getUTCFullYear();
month = utcDateStoredInMongoDB.getUTCMonth();
day = utcDateStoredInMongoDB.getUTCDate();
// Use that year, month, day to initialize a new Date in
// the user's time zone.
dateForDatePicker = new Date(year, month, day);
// Use that for your date picker.
dateForDatePicker.toLocaleDateString();
// => '1/1/2023'
// To go in the other direction, pull out the year/month/day
// in the current time zone, and turn that into a UTC date.
dateReturnedByDatePicker = new Date(2023, 02, 15);
year = dateReturnedByDatePicker.getFullYear();
month = dateReturnedByDatePicker.getMonth();
day = dateReturnedByDatePicker.getDate();
dateToStoreInMongoDB = new Date(Date.UTC(year, month, day));
dateToStoreInMongoDB.toISOString();
// => '2023-03-15T00:00:00.000Z'
Note that this all will get a lot easier in a year or so when the new JavaScript built-in date/time API, called Temporal starts shipping in browsers and Node.js. With Temporal, these kinds of problems are much easier because there's a dedicated API, Temporal.PlainDate for dealing with date-only values.
Luxon is working as intended and the display is correct. What is wrong is the data in your MongoDB.
Most libraries consider current time zone when you parse a date. I live in Switzerland.
const moment = require("moment");
console.log( moment('2023-01-01').toDate() )
> 2022-12-31T23:00:00.000Z
const { DateTime } = require("luxon");
console.log( DateTime.fromISO('2023-01-01').toJSDate() )
> 2022-12-31T23:00:00.000Z
const dayjs = require('dayjs')
console.log( dayjs('2023-01-01').toDate() )
> 2022-12-31T23:00:00.000Z
However, the native JavaScript new Date() constructor does not!
console.log( new Date('2023-01-01') )
> 2023-01-01T00:00:00.000Z
Maybe this behavior depends on your environment and scripting engine, I don't know.
You should also use Luxon when you parse the input data - don't forget to use .toJSDate() to convert the DateTime object back to Javascript native Date object.
Luxon uses the system time zone by default. You can change it:
const { DateTime, Settings } = require("luxon");
Settings.defaultZone = 'America/New_York';
If you don't care about the time, you can also use startOf('day')
Settings.defaultZone = 'America/New_York';
DateTime.now().startOf('day').toJSDate()
> 2023-01-13T05:00:00.000Z
DateTime.now().startOf('day').toISO()
> '2023-01-13T00:00:00.000-05:00'
I'm determining the difference between two calendar dates in Javascript in an Ember app. I'm currently using date-fns's differenceInCalendarDays.
Now that mostly provides the desired results, the only issue is that I need to handle calculating the difference between 2 dates that is sensitive to a timezone (not the local timezone to the browser).
As far as I'm aware JS Dates are tracked as UTC, with no timezone stored on the date object itself. Any timezone localization I've done in JS has been outputting a string.
Is there a good library or way to accomplish differenceInCalendarDays while taking into account the timezone?
const daysAgo = this.intl.formatRelative(-differenceInCalendarDays(new Date(), someOtherDay), {
unit: 'day',
numeric: 'auto',
timeZone: 'this.intl.timeZone
});
This is a small sample of what I'm doing, obviously differenceInCalendarDays will resolve to a number which won't take into account any timeZone. The docs for differenceInDays is timezone sensitive to the browser's local time (which is not helpful here), but differenceInCalendarDays makes no such mention.
Any help would be greatly appreciated!
Logically, the difference between two calendar dates such as 2020-01-01 and 2020-01-02 is not time zone sensitive, nor does it involve time at all. It is exactly one day. In this context a day is not 24 hours, but rather it is a logical division of a year. Think of it as a square on a paper calendar.
However - at any given instant two different time zones might be on the same calendar date, or they might be on two different calendar dates. Thus, a time zone matters when determining the date that it is "now" (or "today", "yesterday", "tomorrow", etc.)
To illustrate both points and hopefully answer your question, the following code can be used to get the number of days passed since "today" in a given time zone:
function daysSince(year, month, day, timeZone) {
// Create a DateTimeFormat object for the given time zone.
// Force 'en' for English to prevent issues with languages that don't use Arabic numerals.
const formatter = new Intl.DateTimeFormat('en', { timeZone });
// Format "now" to a parts array, then pull out each part.
const todayParts = formatter.formatToParts(); // now is the default when no Date object is passed.
const todayYear = todayParts.find(x=> x.type === 'year').value;
const todayMonth = todayParts.find(x=> x.type === 'month').value;
const todayDay = todayParts.find(x=> x.type === 'day').value;
// Make a pseudo-timestamp from those parts, abusing Date.UTC.
// Note we are intentionally lying - this is not actually UTC or a Unix/Epoch timestamp.
const todayTimestamp = Date.UTC(+todayYear, todayMonth-1, +todayDay);
// Make another timestamp from the function input values using the same approach.
const otherTimestamp = Date.UTC(+year, month-1, +day);
// Since the context is the same, we can subtract and divide to get number of days.
return (todayTimestamp - otherTimestamp) / 864e5;
}
// example usage:
console.log("US Pacific: " + daysSince(2020, 1, 1, 'America/Los_Angeles'));
console.log("Japan: " + daysSince(2020, 1, 1, 'Asia/Tokyo'));
This approach only works because UTC doesn't have transitions (such as DST or changes in standard time offset).
Also note that I don't use Date objects here, because we'd have to be very careful about how those objects were constructed. If you only have a Date object coming from a date picker UI, that object was likely created assuming local time - not the time in a particular time zone. So, you'll want to pull out the year, month, and day from that object before continuing. For example:
daysSince(dt.getFullYear(), dt.getMonth() + 1, dt.getDate(), 'America/New_York');
Pay close attention to +1 and -1. The Date object uses 0-based months, but I prefer 1-based.
DOM:
<input id="myTextbox" type="datetime-local" />
Javascript (jQuery):
$('#myTextbox').val(new Date().toISOString());
Doesn't work. The format of input[type=datetime-local] is supposed to be ISO 8601, which is what javascript's Date.toISOString() returns.
Unfortunately, the previous answers did not work properly for me, because they suggest considering UTC time as my local time (which is, generally saying, incorrect).
For example, if my local time is 2021-03-10T01:50:55+0200, then date.toISOString() returns 2021-03-09T23:50:55Z, so I cannot just cut Z at the end, because for datetime-local I need local datetime 2021-03-10T01:50:55, NOT 2021-03-09T23:50:55.
So, the fixed code would be the following:
const d = new Date();
const dateTimeLocalValue = (new Date(d.getTime() - d.getTimezoneOffset() * 60000).toISOString()).slice(0, -1);
$('#myTextbox').val(dateTimeLocalValue);
That's why it works: we still use the trick of removing trailing "Z" from UTC's time format, but before doing it, we shift the time by our time zone offset (returning by date.getTimezoneOffset() in minutes) in the backward direction. After that, the shifted time, converted to UTC, provides the same date & time that our local. Of course, actually, the shifted time is a different moment, but we don't care as soon as its date & time in UTC matches our date & time in the local timezone.
With the example above, it works the following way:
shift local time by timezone offset in opposite direction (e.g. if it was UTC+2, then we make even further from UTC): 2021-03-10T01:50:55+0200 -> 2021-03-10T03:50:55+0200 (by - date.getTimezoneOffset() * 60000, because 1 minute is 60000 milliseconds)
return date&time values back by converting to UTC: 2021-03-10T03:50:55+0200 -> 2021-03-10T01:50:55Z (by .toISOString())
remove trailing Z to get real local time with the suited format for <input type="datetime-local"> (by .slice(0, -1))
If someone needs back transformation, from input value to js Date, then we just need to do the same steps in the reverse order:
const dateTimeLocalValue = $('#myTextbox').val();
const fakeUtcTime = new Date(`${dateTimeLocalValue}Z`);
const d = new Date(fakeUtcTime.getTime() + fakeUtcTime.getTimezoneOffset() * 60000);
console.log(d);
Any questions are welcome)
Update: this answer may set the date incorrectly (off by one day) based on your local time zone and time of day. See Maxim's answer for an explanation and a correct solution.
--
http://www.w3schools.com/jsref/jsref_toisostring.asp:
The toISOString() method converts a Date object into a string, using
the ISO standard.
The standard is called ISO-8601 and the format is:
YYYY-MM-DDTHH:mm:ss.sssZ
While ISO 8601 has some flexibility, the format of javascript's Date's toISOString() is exactly as shown above.
The 'Z' at the end means this is a UTC date. So, this representation includes timezone information. (Javascript dates are naturally in UTC time since they are internally represented as milliseconds since epoch.)
The format of HTML5 input with type=datetime-local must be ...
The following parts, in exactly the following order:
A date.
The literal string "T".
A time.
Example:
1985-04-12T23:20:50.52
1996-12-19T16:39:57
http://www.w3.org/TR/html-markup/input.datetime-local.html
This is still ISO 8601, but stricter, and it does not allow a timezone to be specified.
Luckily, removing the timezone is as easy as removing the trailing 'Z'.
var isoStr = new Date().toISOString();
$('#myTextbox').val(isoStr.substring(0,isoStr.length-1));
Date.toLocaleString can do the trick for you:
$('#myTextbox').val(new Date().toLocaleString("sv-SE", {
year: "numeric",
month: "2-digit",
day: "2-digit",
hour: "2-digit",
minute: "2-digit",
second: "2-digit"
}).replace(" ", "T"));
This will work even in browsers that don't support datatime-local like Firefox-desktop and Safari-desktop.
For more information on date-related-inputs to js-date conversions check this article that I wrote on the topic.
Use $('#myTextbox')[0].valueAsNumber = new Date().getTime().
HTMLInputElement interface also has valueAsDate property, but type=datetime-local doesn't support it unfortunately.
https://html.spec.whatwg.org/C/#input-type-attr-summary
For me, I do like this:
const d = new Date()
element.value = `${d.toLocaleDateString().split("/").reverse().join("-")} ${d.toLocaleTimeString()}`
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Convert date to another timezone in JavaScript
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I am using a JavaScript Date class & trying to get the current date using getDate() method. But obviously it is loading system date & time. I am running the code from India but I want to get the date & time of UK using the same method. How can I do that ?
If you know the UTC offset then you can pass it and get the time using the following function:
function calcTime(city, offset) {
// create Date object for current location
var d = new Date();
// convert to msec
// subtract local time zone offset
// get UTC time in msec
var utc = d.getTime() + (d.getTimezoneOffset() * 60000);
// create new Date object for different city
// using supplied offset
var nd = new Date(utc + (3600000*offset));
// return time as a string
return "The local time for city"+ city +" is "+ nd.toLocaleString();
}
alert(calcTime('Bombay', '+5.5'));
Taken from: Convert Local Time to Another
You could use Intl.DateTimeFormat.
let options = {
timeZone: 'Europe/London',
year: 'numeric',
month: 'numeric',
day: 'numeric',
hour: 'numeric',
minute: 'numeric',
second: 'numeric',
},
formatter = new Intl.DateTimeFormat([], options);
console.log(formatter.format(new Date()));
Alternatively, if you're formatting just once instead of bulk use Date.prototype.toLocaleDateString().
(new Date()).toLocaleString([], options)
Unfortunately browsers are not required to understand timezones other than UTC, so try these blocks and figure out an alternative in case it fails, for example fetch the timezone offset from a server.
One way to do this is to use getLocaleString, like this:
Create a date object:
date = new Date(0)
If you are in Berlin, this should convert to this string:
Thu Jan 01 1970 01:00:00 GMT+0100 (CET)
Get the hours in Athens:
date.toLocaleString('de-DE', {hour: '2-digit', hour12: false, timeZone: 'Europe/Athens' })
'02'
Get the hours in Shanghai:
date.toLocaleString('de-DE', {hour: '2-digit', hour12: false, timeZone: 'Asia/Shanghai' })
'08'
You can use getUTCDate() and the related getUTC...() methods to access a time based off UTC time, and then convert.
If you wish, you can use valueOf(), which returns the number of seconds, in UTC, since the Unix epoch, and work with that, but it's likely going to be much more involved.
This is Correct way to get ##
function getTime(offset)
{
var d = new Date();
localTime = d.getTime();
localOffset = d.getTimezoneOffset() * 60000;
// obtain UTC time in msec
utc = localTime + localOffset;
// create new Date object for different city
// using supplied offset
var nd = new Date(utc + (3600000*offset));
//nd = 3600000 + nd;
utc = new Date(utc);
// return time as a string
$("#local").html(nd.toLocaleString());
$("#utc").html(utc.toLocaleString());
}
If it's really important that you have the correct date and time; it's best to have a service on your server (which you of course have running in UTC) that returns the time. You can then create a new Date on the client and compare the values and if necessary adjust all dates with the offset from the server time.
Why do this? I've had bug reports that was hard to reproduce because I could not find the error messages in the server log, until I noticed that the bug report was mailed two days after I'd received it. You can probably trust the browser to correctly handle time-zone conversion when being sent a UTC timestamp, but you obviously cannot trust the users to have their system clock correctly set. (If the users have their timezone incorrectly set too, there is not really any solution; other than printing the current server time in "local" time)
before you get too excited this was written in 2011
if I were to do this these days I would use Intl.DateTimeFormat. Here is a link to give you an idea of what type of support this had in 2011
original answer now (very) outdated
Date.getTimezoneOffset()
The getTimezoneOffset() method returns the time difference between Greenwich Mean Time (GMT) and local time, in minutes.
For example, If your time zone is GMT+2, -120 will be returned.
Note: This method is always used in conjunction with a Date object.
var d = new Date()
var gmtHours = -d.getTimezoneOffset()/60;
document.write("The local time zone is: GMT " + gmtHours);
//output:The local time zone is: GMT 11
The .getTimezoneOffset() method should work. This will get the time between your time zone and GMT. You can then calculate to whatever you want.
short answer from client-side: NO, you have to get it from the server side.