John Davidson

Message:

I need to know what time zone is currently my users are in based on their IP or http header.

I got many answer regarding this issue, but i could not understood those answer. Some said use -new Date().getTimezoneOffset()/60 (from here). But what does it mean?

I have a date_default_timezone_set("Asia/Calcutta"); in the root of my (index.php) page. So for this I have to get the timezone dynamically and set it in place of Asia/Calcutta.

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My Answer:
To detect the user's timezone based on their IP or HTTP header, you can use a combination of JavaScript and server-side scripting.

One way to do this is to use JavaScript to get the user's timezone offset in minutes using `new Date().getTimezoneOffset()`. This method returns the difference in minutes between UTC time and the local time, with a positive value indicating that the local timezone is behind UTC and a negative value indicating that it is ahead of UTC.

You can then convert this offset to hours by dividing it by 60. For example, if `new Date().getTimezoneOffset()` returns -300, this means the user is in a timezone that is 5 hours behind UTC (since -300 / 60 = -5).

You can then send this timezone offset to your server using an AJAX request or include it in the HTTP headers. Your server-side script can then use this information to determine the user's timezone and set it dynamically.

Alternatively, you can use a service like GeoIP to get the user's location based on their IP address and then determine the timezone from that information. There are also libraries like Moment.js that can help with timezone detection and conversion in JavaScript.

Overall, the key is to use a combination of client-side and server-side techniques to accurately determine the user's timezone based on their location or HTTP headers.