javascript timezone code example

Example 1: javascript set date to timezone

var d = new Date("2020-04-13T00:00:00.000+08:00"); /* midnight in China on April 13th */
d.toLocaleString('en-US', { timeZone: 'America/New_York' });
//=> "4/12/2020, 12:00:00 PM"
// (midnight in China on April 13th is noon in New York on April 12th)

Example 2: get browser timezone javascript

Intl.DateTimeFormat().resolvedOptions().timeZone

Example 3: javascript set date to timezone

function convertTZ(date, tzString) {
    return new Date((typeof date === "string" ? new Date(date) : date).toLocaleString("en-US", {timeZone: tzString}));   
}

// usage: Asia/Jakarta is GMT+7
convertTZ("2012/04/10 10:10:30 +0000", "Asia/Jakarta") // Tue Apr 10 2012 17:10:30 GMT+0700 (Western Indonesia Time)

// Resulting value is regular Date() object
const convertedDate = convertTZ("2012/04/10 10:10:30 +0000", "Asia/Jakarta") 
convertedDate.getHours(); // 17

// Bonus: You can also put Date object to first arg
const date = new Date()
convertTZ(date, "Asia/Jakarta") // current date-time in jakarta.

Example 4: get user time using timezone javascript

function calcTime(city, offset) {
    // create Date object for current location
    var d = new Date();

    // convert to msec
    // subtract local time zone offset
    // get UTC time in msec
    var utc = d.getTime() + (d.getTimezoneOffset() * 60000);

    // create new Date object for different city
    // using supplied offset
    var nd = new Date(utc + (3600000*offset));

    // return time as a string
    return "The local time for city"+ city +" is "+ nd.toLocaleString();
}

alert(calcTime('Bombay', '+5.5'));

Example 5: javascript date timezone

// this example takes 2 seconds to run
const start = Date.now();

console.log('starting timer...');
// expected output: starting timer...

setTimeout(() => {
  const millis = Date.now() - start;

  console.log(`seconds elapsed = ${Math.floor(millis/1000)}`);
  // expected output : seconds elapsed = 2
}, 2000);