Is there a way get the timezone of a user by their latitude and longitude? And not just the offset, but the actual timezone they're in.
Essentially, I'm searching for the polar opposite of DateTimeZone::getLocation which returns the latitude and longitude for a certain timezone.
For those who wants to get timezone from country code, latitude and longitude. ( easy to get it if you have a geoip module installed on your server )
Try this, I've added a distance calculation - only for those countries which has multiple timezones. Ah, and the country code is a two letter ISO code.
// ben@jp
function get_nearest_timezone($cur_lat, $cur_long, $country_code = '') {
$timezone_ids = ($country_code) ? DateTimeZone::listIdentifiers(DateTimeZone::PER_COUNTRY, $country_code)
: DateTimeZone::listIdentifiers();
if($timezone_ids && is_array($timezone_ids) && isset($timezone_ids[0])) {
$time_zone = '';
$tz_distance = 0;
//only one identifier?
if (count($timezone_ids) == 1) {
$time_zone = $timezone_ids[0];
} else {
foreach($timezone_ids as $timezone_id) {
$timezone = new DateTimeZone($timezone_id);
$location = $timezone->getLocation();
$tz_lat = $location['latitude'];
$tz_long = $location['longitude'];
$theta = $cur_long - $tz_long;
$distance = (sin(deg2rad($cur_lat)) * sin(deg2rad($tz_lat)))
+ (cos(deg2rad($cur_lat)) * cos(deg2rad($tz_lat)) * cos(deg2rad($theta)));
$distance = acos($distance);
$distance = abs(rad2deg($distance));
// echo '<br />'.$timezone_id.' '.$distance;
if (!$time_zone || $tz_distance > $distance) {
$time_zone = $timezone_id;
$tz_distance = $distance;
}
}
}
return $time_zone;
}
return 'unknown';
}
//timezone for one NY co-ordinate
echo get_nearest_timezone(40.772222,-74.164581) ;
// more faster and accurate if you can pass the country code
echo get_nearest_timezone(40.772222, -74.164581, 'US') ;
A good resource is the Google Time Zone API.
Documentation: https://developers.google.com/maps/documentation/timezone/
It takes latitude and longitude and returns array like this:
array(
'dstOffset' => (int) 3600,
'rawOffset' => (int) -18000,
'status' => 'OK',
'timeZoneId' => 'America/New_York',
'timeZoneName' => 'Eastern Daylight Time'
)
...but there are some limits:
[updated 2019] The Google Time Zone API has usage limits in place. Basically, billing must be enabled on your project, but a $200 USD "Google Maps Platform credit" is applied each month (so in most cases your first 40,000 Time Zone API calls/month would be free of charge).
I did a timezone solution recently in an 8 hour long hackathon. It's quickly put together and I'd love to develop it further and sell it as a product but since there is no way for me to do it, I've open sourced it at my github.
There is a demo too but it may go down if it hits resource limits. It's a free webapp on Google App Engine.
You can definitely optimize/augment this further in wrt - running time, space, data - to suit your needs.
The Yahoo places API provides timezone information via reverse geolocation.
Check it out.
http://developer.yahoo.com/geo/placefinder/guide/requests.html
How about finding the closest point to the one in the list of all timezone locations? I wonder how accurate is this?
UPDATE: Eventually, I came up with this snippet that works for me. This will work fine for all locations, but may not be accurate for those close to borders.
/**
* Attempts to find the closest timezone by coordinates
*
* @static
* @param $lat
* @param $lng
*/
public static function getClosestTimezone($lat, $lng)
{
$diffs = array();
foreach(DateTimeZone::listIdentifiers() as $timezoneID) {
$timezone = new DateTimeZone($timezoneID);
$location = $timezone->getLocation();
$tLat = $location['latitude'];
$tLng = $location['longitude'];
$diffLat = abs($lat - $tLat);
$diffLng = abs($lng - $tLng);
$diff = $diffLat + $diffLng;
$diffs[$timezoneID] = $diff;
}
//asort($diffs);
$timezone = array_keys($diffs, min($diffs));
return $timezone[0];
}
