Determine timezone from latitude/longitude without

Question

is there any possibility to determine the timezone of point (lat/lon) without using webservices? Geonames.org is not stable enough for me to use :( I need this to work in PHP.

Thanks

Answer 1

I've written a small Java class to do this. It could be easily translated to PHP. The database is embedded in the code itself. It's accurate to 22km.

https://sites.google.com/a/edval.biz/www/mapping-lat-lng-s-to-timezones

The whole code is basically stuff like this:

         if (lng < -139.5) {
          if (lat < 68.5) {
           if (lng < -140.5) {
            return 371;
           } else {
            return 325;
           }

...so I presume a translation to PHP would be easy.

Answer 2

You can get the timezone based on the location in javascript.

function initAutocomplete() {
        // Create the autocomplete object, restricting the search to geographical
        // location types.
        autocomplete = new google.maps.places.Autocomplete(
                /** @type {!HTMLInputElement} */(document.getElementById('Location')),
                {types: ['geocode']});

        // When the user selects an address from the dropdown, populate the address
        // fields in the form.
        autocomplete.addListener('place_changed', fillInAddress);
    }

    function fillInAddress() {
        // Get the place details from the autocomplete object.
        var place = autocomplete.getPlace();

        fnGettimezone($('#Location').serialize());
        for (var component in componentForm) {
            document.getElementById(component).value = '';
            document.getElementById(component).disabled = false;
        }

        // Get each component of the address from the place details
        // and fill the corresponding field on the form.
        for (var i = 0; i < place.address_components.length; i++) {
            var addressType = place.address_components[i].types[0];
            if (componentForm[addressType]) {
                var val = place.address_components[i][componentForm[addressType]];
                document.getElementById(addressType).value = val;
            }
        }

    }


function fnGettimezone(location) {
    $.ajax({
            url: "http://maps.googleapis.com/maps/api/geocode/json?address=" + location + "&sensor=false",
            dataType: 'json',
            success: function (result) {
                 console.log(result);
                // result is already a parsed javascript object that you could manipulate directly here
                var myObject = JSON.parse(JSON.stringify(result));
                lat = myObject.results[0].geometry.location.lat;
                lng = myObject.results[0].geometry.location.lng;
                console.log(myObject);

                $.ajax({
                    url: "https://maps.googleapis.com/maps/api/timezone/json?location=" + lat + "," + lng + "&timestamp=1331161200&sensor=false",
                    dataType: 'json',
                    success: function (result) {
                        // result is already a parsed javascript object that you could manipulate directly here
                        var myObject = JSON.parse(JSON.stringify(result));
                        $('#timezone').val(myObject.timeZoneName);

                    }
                });

            }
        });
    }

Answer 3

Unfortunately, time zones are not regular enough for some simple function. See the map in Wikipedia - Time Zone

However, some very rough approximation can be calculated: 1 hour difference corresponds to 15 degrees longitude (360 / 24).

Answer 4

You can use Google Timezone api. https://maps.googleapis.com/maps/api/timezone/json?location=39.6034810,-119.6822510&timestamp=1331161200&key=YOUR_API_KEY

{
   "dstOffset" : 0,
   "rawOffset" : -28800,
   "status" : "OK",
   "timeZoneId" : "America/Los_Angeles",
   "timeZoneName" : "Pacific Standard Time"
}

Answer 5

How exact do your results have to be? If a rough estimate is enough, calculate the offset yourself:

offset = direction * longitude * 24 / 360

where direction is 1 for east, -1 for west, and longitude is in (-180,180)

Answer 6

Not sure if this is useful or not, but I built a database of timezone shapes (for North America only), which is painstakingly accurate and current not just for borders, but also for daylight saving time observance. Also shapes for unofficial exceptions. So you could query the set of shapes for a given location could return multiple shapes that apply to that location, and choose the correct one for the time of year.

You can see an image of the shapes at http://OnTimeZone.com/OnTimeZone_shapes.gif. Blue shapes are around areas that do not observe daylight saving time, magenta shapes those that do observe daylight saving time, and neon green shapes (small and tough to see at that zoom level) are for areas with unofficial deviation from the official time zone. Lots more detail on that available at the OnTimeZone.com site.

The data available for download at OnTimeZone.com is free for non-commercial use. The shape data, which is not available for download, is available for commercial license.