How to Automatically Detect User's Timezone

How to automatically detect user's timezone?

Use javascript solution

http://www.onlineaspect.com/2007/06/08/auto-detect-a-time-zone-with-javascript/

Demo should show your timezone in select box.

http://onlineaspect.com/examples/timezone/index.html (Dead link)

Automatically detect user's current local time with JavaScript or PHP

In short no.

I would suggest using server side time, and have the ability for the user to choose their time zone.

You could possibly calculate default time zones for users based on heuristics around their IP address, but this is open to error.

You should be able to extract client side time zone information through javascript / Ajax, but as with the time itself this is also open to error.

My recommendation: Let users choose their time zone with a sensible default based on where you expect your users to be.

How to detect user's timezone?

To summarize Matt Johnson's answer in terms of code:

<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js">
</script>
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/jstimezonedetect/1.0.4/jstz.min.js">
</script>
<script type="text/javascript">
  $(document).ready(function(){
    var tz = jstz.determine(); // Determines the time zone of the browser client
    var timezone = tz.name(); //For e.g.:"Asia/Kolkata" for the Indian Time.
    $.post("url-to-function-that-handles-time-zone", {tz: timezone}, function(data) {
       //Preocess the timezone in the controller function and get
       //the confirmation value here. On success, refresh the page.
     });
  });
</script>

get client time zone from browser

Look at this repository pageloom it is helpful

download jstz.min.js and add a function to your html page

<script language="javascript">
    function getTimezoneName() {
        timezone = jstz.determine()
        return timezone.name();
    }
</script>

and call this function from your display tag

Does Django automatically detect the end user's timezone?

Django doesn't detect end user's timezone. It saves the objects in the database in UTC time.

Then you can convert the UTC time to the client's time on the browser using JavaScript for displaying.

Django also provides methods to convert timezones on the server for a particular request or a session: See docs. However, using JavaScript is definitely the easier option.

Django also has a TIME_ZONE setting. But this is very limited. Django uses this timezone for displaying the time in admin or other places. It's very limited because only one timezone is supported, and it won't change depending upon the client's timezone.

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Converting UTC to localtime on a user's browser using JavaScript is the best and easiest solution.

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Note: The older version of this answer (which was marked accepted) can be found here.

Autodetect and prompt when device timezone is changed in angular7

How to autodetect and prompt user that his device timezone has changed and is different from profile/saved timezone?

Time zone detection is covered in this answer. There are multiple approaches, but ultimately you want to get the IANA time zone identifier (such as America/New_York) to compare against your saved value in the user's profile.

How to get list of available timezones...

JavaScript doesn't have a built-in method for this, but you can use a library. For example, Moment-timezone provides the moment.tz.names() function, and Date-fns-timezone provides the listTimeZones() function.

... This timezone list should be same for all devices like web, android and ios device.

While most environments use IANA time zone identifiers, there is no guarantee that all devices will have fully updated data. Say a new time zone is introduced and your devices detect it - if your server-side platform doesn't have the latest time zone data, then you might encounter an error. The best thing you can do here is to make sure you regularly check for updates, which varies depending on platform.

... some timezone returns "Asia/Kolkata" and "Asia/Calcutta"

That is fine. Asia/Kolkata is the prefered canonical zone, and Asia/Calcutta is a link (or alias) of that zone. All modern platforms should be able to interpret either. If you're trying to do this yourself, you'll need to be sure to resolve links to their canonical zones before comparing. There are libraries that can do this for you.

Getting the client's time zone (and offset) in JavaScript

Using getTimezoneOffset()

You can get the time zone offset in minutes like this:

var offset = new Date().getTimezoneOffset();
console.log(offset);
// if offset equals -60 then the time zone offset is UTC+01

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