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.
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>
date_default_timezone_set(timezone) which returns false if timezone is invalid! Using this retrun value he has to decide whether or not to refresh the page!
Intl.DateTimeFormat().resolvedOptions().timeZone instead of an entire library.Time zone information of the browser is not part of the HTTP spec, so you can't just get it from a header.
If you have location coordinates (from a mobile device GPS, for example), then you can find the time zone using one of these methods. However, geolocation by IP address is not a great solution because often the IP is that of an ISP or proxy server which may be in another time zone.
There are some strategies you can use to try to detect the time zone, such as using jsTimeZoneDetect library, which is a great starting point, but imperfect enough that you can't just rely on that alone. If you're using moment.js, there's a built in function in moment-timezone called moment.tz.guess() that does the same thing.
UPDATE: In modern browsers, you can get the full time zone ID with Intl.DateTimeFormat().resolvedOptions().timeZone which was not available when this answer was originally written.
The idea of using JavaScript's getTimezoneOffset() function is flawed in that you are not getting a time zone - just a single offset for a particular date. See the TimeZone tag wiki's section titled "TimeZone != Offset".
However you look at it, ultimately you have to decide on one of two approaches:
OR
I discuss this in more detail (from a c# perspective) in this answer.
Dependencies:
http://geolite.maxmind.com/download/geoip/database/GeoLiteCity.dat.gz
//Get remote IP
$ip = $_SERVER['REMOTE_ADDR'];
//Open GeoIP database and query our IP
$gi = geoip_open("GeoLiteCity.dat", GEOIP_STANDARD);
$record = geoip_record_by_addr($gi, $ip);
//If we for some reason didnt find data about the IP, default to a preset location.
if(!isset($record)) {
$record = new geoiprecord();
$record->latitude = 59.2;
$record->longitude = 17.8167;
$record->country_code = 'SE';
$record->region = 26;
}
//Calculate the timezone and local time
try {
//Create timezone
$user_timezone = new DateTimeZone(get_time_zone($record->country_code, ($record->region!='') ? $record->region : 0));
//Create local time
$user_localtime = new DateTime("now", $user_timezone);
$user_timezone_offset = $user_localtime->getOffset();
}
//Timezone and/or local time detection failed
catch(Exception $e) {
$user_timezone_offset = 7200;
$user_localtime = new DateTime("now");
}
echo 'User local time: ' . $user_localtime->format('H:i:s') . '<br/>';
echo 'Timezone GMT offset: ' . $user_timezone_offset . '<br/>';
One solution is to ask them! Especially on members systems where you can capture/register a user - give them a choice at that point. Simple but accurate.
This works fine...
echo <<<EOE
<script type="text/javascript">
if (navigator.cookieEnabled)
document.cookie = "tzo="+ (- new Date().getTimezoneOffset());
</script>
EOE;
if (!isset($_COOKIE['tzo'])) {
echo <<<EOE
<script type="text/javascript">
if (navigator.cookieEnabled) document.reload();
else alert("Cookies must be enabled!");
</script>
EOE;
die();
}
$ts = new DateTime('now', new DateTimeZone('GMT'));
$ts->add(DateInterval::createFromDateString($_COOKIE['tzo'].' minutes'));
Timezone is not available in the HTTP header, but country (abbreviation) is in the ACCEPT_LANGUAGE header. It'll be something like "en-US" (US is the country code). This can be combined with the JavaScript information to get a good idea of the user's timezone.
This is what I'm using in JS:
function timezone() {
var now = new Date();
var jano = new Date(now.getFullYear(), 0, 1).getTimezoneOffset()/-60;
var julo = new Date(now.getFullYear(), 6, 1).getTimezoneOffset()/-60;
var tz = Math.min(jano, julo);
if (jano != julo) tz += ((jano < julo) ? 'S' : 'W') + Math.abs(jano - julo);
return tz;
}
This returns a string like "-6S1" for the central zone (standard time offset of -6 hours, DST active in the summer and adds 1 hour). I use a cookie to make this available to PHP. PHP searches the TZ database for zones that match this, and the country. For here (US, -6S1) there are 7 matching zones, the first is "America/Chicago".
BTW, there are 2 zones in the database where DST adds something other than 1 hour: Lord Howe Island (10.5W0.5) and Troll Station, Antarctica (0W2).
A more modern answer to this question is to put a javascript function on your landing page that sends the information to your PHP backend. I've put in some debugging and verbose options for beginners to use.
<script>
// Function to send the timezone to the server
function setTimezoneOnPageLoad() {
const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone; // Get the user's timezone
// Make the AJAX request
fetch('/set-timezone', {
method: 'POST', // Use POST for sending data
headers: {
'Content-Type': 'application/json', // Inform the server we're sending JSON
},
body: JSON.stringify({ timezone: timezone }), // Send the timezone as JSON
})
.then(response => {
if (!response.ok) {
throw new Error(`HTTP error! Status: ${response.status}`);
}
return response.json(); // Parse JSON response
})
.then(data => {
// Check the success flag in the JSON response
if (data.success) {
console.log(`Success: ${data.message}`);
} else {
console.error(`Error: ${data.error}`);
}
})
.catch(error => {
// Catch and log any errors
console.error('AJAX request failed:', error);
});
}
// Fire the function when the page is fully loaded
document.addEventListener('DOMContentLoaded', setTimezoneOnPageLoad);
</script>
Then on the php receiving this call (in this example /set-timezone is the route to your php code):
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
header('Content-Type: application/json'); // Set the correct response type
$data = json_decode(file_get_contents('php://input'), true);
session_start();
$_SESSION['timezone']='';
if (!empty($data['timezone'])) {
$timezone = htmlspecialchars($data['timezone'], ENT_QUOTES, 'UTF-8');
// Validate and set the timezone
if (in_array($timezone, timezone_identifiers_list())) {
date_default_timezone_set($timezone);
// Send a structured response
echo json_encode([
'success' => true,
'message' => "Timezone set successfully.",
'timezone' => $timezone,
]);
$_SESSION['timezone']=$timezone
} else {
echo json_encode([
'success' => false,
'error' => "Invalid timezone.",
]);
}
} else {
echo json_encode([
'success' => false,
'error' => "Timezone not provided.",
]);
}
exit;
}
Now your backend can keep track of this user's session timezone in $_SESSION['timezone']. You can see where this is supported here https://caniuse.com/?search=Intl.DateTimeFormat().resolvedOptions().timeZone for about 96% of all global browsers.
