How to use the latitude and longitude to get local time, not the server time?

HsuKao-Ming · ‎08-21-2018

hey guyts,

because I can't find how to use the latitude and longitude to get local time,

The original method is to use the timezone through google to get the offset for daylight-savings time.

I want to solve this problem.

SteveCole · ‎08-21-2018

ESRI does have a World Time Zone layer in the Living Atlas. Query your lat/long point against that service to find out what the time offset is to get your local time.

HsuKao-Ming · ‎08-21-2018

Steve,

How can I use that for javascript or json?

SteveCole · ‎08-22-2018

You would use Query & QueryTask similar to what's shown in this example. The example uses the location where you click on the map but in your case, you would create a point using your lat/long values and then pass that as the value used with query.Geometry.

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no"/>
    <title>Simple Map</title>
    <link rel="stylesheet" href="https://js.arcgis.com/3.25/esri/css/esri.css">
    <style>
      html, body, #map {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
    <script src="https://js.arcgis.com/3.25/"></script>
    <script>
      var map;

      require(["dojo/on","esri/map","esri/layers/FeatureLayer","esri/tasks/query", "esri/tasks/QueryTask","dojo/domReady!"], function(on,Map,FeatureLayer,Query,QueryTask) {
        map = new Map("map", {
          basemap: "topo",  //For full list of pre-defined basemaps, navigate to http://arcg.is/1JVo6Wd
          center: [-100.45, 37.75], // longitude, latitude
          zoom: 4
        });
        var featureLayer = new FeatureLayer("https://services.arcgis.com/P3ePLMYs2RVChkJx/ArcGIS/rest/services/World_Time_Zones/FeatureServer/0",{opacity:0.5});

        map.addLayer(featureLayer);
        
        map.on("click", function(evt){
            var queryTask = new QueryTask("https://services.arcgis.com/P3ePLMYs2RVChkJx/ArcGIS/rest/services/World_Time_Zones/FeatureServer/0");
            var query = new Query();
            query.geometry = evt.mapPoint;
            query.outFields = ["*"];
            queryTask.on("complete", processResults);
            queryTask.execute(query);
            
            function processResults(results) {
              var features = results.featureSet.features;
              if (features.length > 0) {
                alert('The zone offset for the clicked location is ' + features[0].attributes.ZONE);
              };              
            };
        });
        
      });
    </script>
  </head>

  <body>
    <div><h2>Click on the map to get the time zone offset</h2></div>
    <div id="map"></div>
  </body>
</html>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

SteveCole · ‎08-22-2018

I tried to update my sample to actually return the local time at the location clicked but I'm having trouble doing so. It's returning the time but off one hour so I don't know if that's due to daylight savings or GMT being 0, etc. Perhaps a more savvy coder can find the error of my ways.

Here's an updated processResults function that returns the timezone offset and the local time (but off by one hour):

            function processResults(results) {
              var features = results.featureSet.features;
              if (features.length > 0) {
                var timeOffset = features[0].attributes.ZONE;
                var curDate = new Date();
                curDate.setUTCMinutes(curDate.getUTCMinutes() + (timeOffset*60));
                
                var hours = curDate.getUTCHours();
                var minutes = curDate.getUTCMinutes();
                var ampm = hours >= 12 ? 'pm' : 'am';
                hours = hours % 12;
                hours = hours ? hours : 12; // the hour '0' should be '12'
                minutes = minutes < 10 ? '0'+minutes : minutes;
                var strTime = hours + ':' + minutes + ' ' + ampm;
  
                alert('The zone offset for the clicked location is ' + features[0].attributes.ZONE + '\n and the local time is ' + strTime); //curDate.toUTCString());
              };              
            };‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍