Use the getTimezoneOffset() method to determine if the current time zone is daylight saving time.

Oct 22, 2021#js47

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This article discusses the use of the getTimezoneOffset() method in JavaScript to determine if the current time zone is in daylight saving time. The getTimezoneOffset() method returns the time difference in minutes between UTC time and local time. It is explained that UTC is the standard world time, equivalent to GMT. The article provides an example code snippet to calculate the time difference between the local time zone and the standard time zone. It is mentioned that a time difference of 480 minutes (8 hours) indicates that the time zone is in the GMT+8 time zone, which is the case for Beijing. The article then demonstrates how to use the getTimezoneOffset() method to determine if the current time zone is in daylight saving time by comparing the time zone offsets of two different dates. The result of the example code indicates that the current time zone is not in daylight saving time.

The getTimezoneOffset() method returns the time difference between UTC time and local time in minutes.

Coordinated Universal Time (UTC) is the time standard set by the world, and UTC time is the same as Greenwich Mean Time (GMT).

Check the time difference between my time zone and the standard time zone.

function myDate () {
  var d = new Date();
  var n = d.getTimezoneOffset();
  console.log(n)
}
myDate();

// PS E:\demo> node 1.js
// -480

That is 480 minutes (8 hours). Beijing time is in the UTC+8 time zone, which is exactly 8 hours ahead of Greenwich Mean Time. This indicates that the getTimezoneOffset() method is effective.

Next, use this method to determine whether the current time zone is daylight saving time.

const time1 = new Date(2021, 0, 1);
const time2 = new Date(2021, 6, 1);
if (time1.getTimezoneOffset() != time2.getTimezoneOffset()) {
  console.log('Daylight saving time');
}
else {
  console.log('Not daylight saving time');
}


// PS E:\demo> node 1.js
// Not daylight saving time