How to create Javascript Date() object given Country ISO code? - javascript

Consider I'm from India and my Country ISO code is IN or IND or 356 (http://en.wikipedia.org/wiki/ISO_3166-1). How could I generate a JavaScript Date object with that? That is, in IST.
In Python, we have astimezone(). Anything similar to that is available in JavaScript?
PS: jQuery or any trusted third party API is allowed.

JavaScript in the browser is not a timezone aware language. It has the ability to work with only two timezones: UTC and local timezone where local timezone depends on the timezone of the Browser or the Operating System that the Browser runs on.
If your browser (and your user's browser) is set to IST, then all dates will display in IST. If your browser is not set to IST, then you're sort of out of luck.
Now, you can do some tricks. For example, you can do the following:
var d = new Date(); // creates a date in user's local timezone
var istD = new Date(d.getTime() + (d.getTimezoneOffset() + 330) * 60000)
// 330 is the IST offset (5h 30m == 330m)
istD is now a date object that will "print the date in IST". Note that this date object is still in the user's local timezone, but as long as you don't display the timezone part, it will appear to be in IST.
There is a small problem with Daylight Saving Time. Since IST does not have DST, this problem is minimized, but still exists if the user's local timezone has DST and you are just a few hours off from the DST offset. You might be able to play around with the Date.getUTC* functions to circumvent the DST issues, however always remember that there is no way to correctly do timezones in clientside JavaScript. There is no library in existence today that correctly handles all TimeZone rules, including Daylight Savings rules for all historical dates.

You can set the date with UTC and then you can convert it into LocaleString. You can see Date.prototype.toLocaleString() for more refrence.
And you can also see the question asked on stack overflowHow do I display a date/time in the user's locale format and time offset?.
Thanks

There is no directly API.But you can coding it by your self.
<html>
<body onload="getTimeByTimeZone(5.5)">
<script type="text/javascript">
function getTimeByTimeZone(offset){
var d = new Date()
localTime = d.getTime();
localOffset=d.getTimezoneOffset()*60000;
utcTime=localTime + localOffset;//get utc time
st=utcTime+3600000*offset;//get the specified timezone time
stime=new Date(st);
document.write("The specified time is :"+stime.toString());
}
</script>
</body>
</html>
Hope this code is helpful to you.

Related

How to show local times for an international virtual conference program, using JavaScript

I have to publish an online program for an international conference. Rather than just showing the date and time of each event according to our timezone (UTC+11), I want the page to display them according to the user's timezone. When the page loads it should show what the server thinks the user's timezone is, but give the user the opportunity to override it, using a dropdown.
I have managed to get this to work:
<script>
function convertTZ(date, tzString) {
return new Date((typeof date === "string" ? new Date(date) : date).toLocaleString("en-US", {timeZone: tzString}));
}
</script>
<body onload = "document.getElementById('datetime').innerHTML = convertTZ('2021/01/09 11:00:00 +1100','Europe/Paris')">
<p id="datetime"></p>
</body>
But how to I get the user’s timezone string and allow the user to override this?
I also will need to extract just the date + time without the timezone info (eg "GMT+1100 (Australian Eastern Daylight Time)") but hopefully I can work that out myself.
(I am very much a JavaScript beginner.)
Any help would be greatly appreciated, particularly if someone knows of something that already exists, which I could adapt. Thanks.
A few things:
You should specify the time of the event in ISO 8601 format: 2021-01-09T11:00:00+11:00.
Or rather, more accurately stated, it should be in the ECMAScript Date Time String Format, such that it is understood unambiguously by all implementations.
2021-01-09T11:00:00+11:00 is compliant with both.
2021/01/09 11:00:00 +1100 is not compliant, and thus would be considered non-standard, implementation-specific, and possibly fail in some browsers.
To use the user's time zone, do not specify a timeZone option to toLocaleString. The default is the user's time zone already.
You should also not supply a locale (en-US), as the formatting of toLocaleString will use the user's locale settings by default. If you want to supply other options, you can pass undefined for the locale to keep the user's default locale intact.
You might want to include the timeZoneName option (either long or short) to display a human-readable time zone description in the output. That will make it clearer for your user to understand the context of the information being displayed.
In the end, you probably want something similar to:
function loadDateTime() {
const eventTime = new Date("2021-01-09T11:00:00+11:00");
const display = eventTime.toLocaleString(undefined, { timeZoneName: 'long' });
document.getElementById('datetime').innerHTML = display;
}
<body onload="loadDateTime()">
<p id="datetime"></p>
</body>
For me, it outputs: 1/8/2021, 4:00:00 PM Pacific Standard Time. You will get a different result depending on your locale and time zone.

Legit javascript UTC Date

I've been looking for a way to keep my dates in UTC in my JS application; however, in every case the Date's getTimezoneOffset() does not return a 0 which, I would imagine, should be the case -- and which would be seemingly important in casting dates between UTC and the local TZ.
See below examples of what I've tried, thanks in advance for any insight!
var TheDate = new Date( Date.UTC(2012, 10, 5) );
console.log(TheDate.getTimezoneOffset()) // => 300 (for me)
console.log(moment().utc().toDate().getTimezoneOffset()) // => 240 (for me)
ECAMScript Dates are inherently UTC and are just an offset from the ECMAScript epoch (a time value in milliseconds from 1970-01-01T00:00:00Z), nothing more. They have no associated timezone.
The host timezone offset is used:
When creating a Date to determine the equivalent UTC time and calculate the time value
In various methods that use local dates and times, such as getHours (vs getUTCHours)
The date itself does not know anything about timezones.
The value returned by getTimezoneOffset is based on the host system settings, the only relationship it has to the Date it's called on is that the offset is calculated for that Date. The method might be called getHostSystemTimezoneOffset, because that's what it returns.
In your code:
new Date(Date.UTC(2012, 10, 5))
creates a Date for 2012-11-05T00:00:00Z. Calling getTimezoneOffset on that date returns the host system offset for the equivalent local date and time, not the offset that was used in creating the Date.
There is no way to associate a timezone with a date without using a library (either one you write or one of the many existing libraries).
In your second example:
moment().utc()
just sets a flag to tell moment.js methods to use UTC for everything. Then using:
....toDate().getTimezoneOffset()
returns a Date object, then gets the host system timezone offset for that date as if you'd done:
new Date().getTimezoneOffset()
If you want to only use UTC, then use UTC methods for everything and ignore timezones completely (which I think is what you want to do).

Want to get Timezone using jquery

In jquery,
var date = new Date();
It is taking system Date Not site Time zone
var date = (new Date()).getTimezoneOffset();
it is also not working.please anyone help for this.thank you.
Return the timezone difference between UTC and Local Time:
var d = new Date()
var n = d.getTimezoneOffset();
The result n will be:
-300
The getTimezoneOffset() method returns the time difference between UTC time and local time, in minutes.
For example, If your time zone is GMT+2, -120 will be returned.
Note: The returned value is not a constant, because of the practice of using Daylight Saving Time.
Tip: The Universal Coordinated Time (UTC) is the time set by the World Time Standard.
Note: UTC time is the same as GMT time.
jQuery has only one date/time function, which is $.now()
If you meant JavaScript, the answer is still no. You can only obtain a time zone offset from date.getTimezoneOffset(). You can't get a time zone - at least not in all browsers.
You can guess at the time zone, by using the jsTimeZoneDetect library, but it is just a guess. It may or may not be accurate.
If you can guarantee your users are running a browser that supports the brand new ECMAScript Internationalization API, you can get the user's time zone with:
Intl.DateTimeFormat().resolvedOptions().timeZone

Get the web User's timezone as string

I am making a site, and where the users will be uploading questions and answers in it. Now I need to get the user's timezone which i can store it in variable $TimeZoneNameTo instead of just "Asia/Kathmandu". is there anyway, where the time zone as a string will be detected and stroed in variable $TimeZoneNAmeTo, so for any user of any timezone, the datetime will be converter to his/her timezone instead of UTC while displaying.
$TimeZoneNameFrom="UTC";
$TimeZoneNameTo="Asia/Kathmandu";
echo "uploaded on".$upload_date;
echo"<br>";
echo date_create($upload_date, new DateTimeZone($TimeZoneNameFrom))
->setTimezone(new DateTimeZone($TimeZoneNameTo))->format("Y-m-d H:i:s");
If all you want to do is present times based on the user's system settings, then just send UTC time values to the client. The value should be milliseconds since 1970-01-01T00:00:00Z. UNIX uses seconds since the same epoch, so you just need a UNIX UTC timestamp multiplied by 1000:
var newLocalDate = new Date(UNIXutcTimeValue * 1000);
Now just present it in a user readable form, say using Date.prototype.toLocaleString:
alert(newLocalDate.toLocaleString());
e.g. 2014-06-06T12:00:00Z is 1402056000 seconds or 1402056000000 milliseconds, so in Safari:
alert(new Date(1402056000000).toLocaleString()) // 6 June 2014 20:00:00 AWST
Of course you can always use Date methods to format the string anyway you want.
Answering the question you ask :
On modern browsers you can fetch the timezone client side using
var tz = Intl.DateTimeFormat().resolved.timeZone;
If your browser doesn't have Intl (IE10- and Safari), then it's a little more complicated. I made a small library for that using moment.js : https://github.com/Canop/tzdetect.js
Answering the problem you have :
Most of the times you don't have to know the client's timezone and you can simply let his browser format a UTC timestamp you send. See RobG's answer.

In Javascript / NodeJS return current date adjusting for timezone, then find UTC equivalent of user's time at 6am

Sorry if the title is a little convoluted. I'm bashing my head against the floor with times in NodeJS / Javascript. I can get the current UTC time like this:
var currentTime = Date.now();
I can get the current time for a user who is, for example, in the -3 timezone like this:
var offsetTime = Date.now() + (numTimeZone * 3600000);
But how do I get the local user time at, say, 6am, converted to UTC?
Practical application:
What I'm trying to do is create an auto-emailer which sends an email to a user at 6am in their local time. My server is in one timezone and they will be in another, so I'm trying to standardise it against UTC so every minute I can set my server to check the currentUTC time, then check what the user's 6am time is converted to UTC (local6am), and if the currentUTC > local6am then an email should be sent.
What's the best way to achieve this? Preferably without using a library if possible.
Utc to Local
moment.utc('2014-02-19 05:24:32 AM').toDate();
Local to utc
Read this documentation.
MomentJS is parsing the date as a locale date-time. If no hour is given, it is assuming midnight.
Then, you convert it to UTC, so it is shifted, according to your local time, forward or backwards. If your are in UTC+N, then you will get the previous date.
moment(new Date('02-19-2014')).utc().format("YYYY-MM-DD HH:mm").toString()
moment(new Date('02-19-2014 12:00')).utc().format("YYYY-MM-DD HH:mm").toString()
(or)
You can try this:
moment.utc('07-18-2013', 'MM-DD-YYYY')
moment.utc('07-18-2013', 'MM-DD-YYYY').format('YYYY-MM-DD')
You do not need to call toString explicitly.

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