Shift in seconds from UTC to real clock time

Question

While fetching data from a weather API the result time zone for Indian location was 19800, which was shift in seconds from UTC to real clock time.

timezone : 19800

I need that to real clock time. ChatGPT gave me this:

var shiftInSeconds = 19800;

var currentTimeUTC = Date.now();
var shiftedTime = currentTimeUTC + (shiftInSeconds * 1000); // Convert seconds to milliseconds
var shiftedDate = new Date(shiftedTime);
var localTime = shiftedDate.toLocaleString();

console.log("Real time:", localTime);

I got the result as

Real time: 17/05/2024, 21:27:43

The actual time now is 03:57 PM. Is there any way to get the exact local clock time ?

Answer 1

maybe like this ?

const newDate = new Date();
const myDate = newDate.toLocaleTimeString("en-IN");
console.log(timedDate);

output : "12:46:20 pm" witch is the real time for me.

Answer 2

This answer is based on your comment:

want to display the corresponding local time at the weather location regardless of the user's own time zone. The API provides time as an offset from UTC

The offset from UTC is not the time, it's the bias between UTC and the local time of the location - the time will be in a separate field in the response, or was provided in your request, and is usually in terms of UTC.

You do not need to shift the time by the offset with math. Doing so can lead to many other errors. You can instead provide the original UTC-based timestamp (as presumably returned by your weather API), and format it to a string in a given fixed offset using the timeZone option of toLocaleString (and similar Intl functions).

You do however, need to convert the offset from a number of seconds to an ISO 8601 compliant time zone offset string.

// Formats a Unix timestamp (in terms of milliseconds) to a string,
// to a fixed time zone offset (in terms of seconds).
function formatTimestamp(ts, offsetSeconds) {
    const lang = undefined; // use the current language
    const timeZone = formatOffset(offsetSeconds);
    return new Date(ts).toLocaleString(lang, { timeZone, timeZoneName: 'long' }); 
}

// Converts offset in seconds to string in ISO 8601 extended format.
// Example: 19800 => "+05:30"
function formatOffset(offsetSeconds) {
    const sign = offsetSeconds < 0 ? '-' : '+';
    const seconds = Math.abs(offsetSeconds);
    const hours = Math.floor(seconds / 3600);
    const minutes = Math.floor((seconds % 3600) / 60);
    return sign + ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2);
}

// The current time at UTC+05:30
console.log(formatTimestamp(Date.now(), 19800));

// A specific time at UTC-08:00
console.log(formatTimestamp(1704067200000, -28800));

I included timeZoneName: 'long' only for demonstration purposes. You can control the format of the output string using any of the options covered in the docs.

Answer 3

Does this work for you ?

I'm forcing the object to print the UTC time (even though in your case the time zone was manually shifted to Indian Standard Time).

The internal time representation is accurate already. It's just the way you printed it.

var shiftInSeconds = 19800;

var currentTimeUTC = Date.now();
var shiftedTime = currentTimeUTC + (shiftInSeconds * 1000); // Convert seconds to milliseconds
var shiftedDate = new Date(shiftedTime);
var localTime = shiftedDate.toLocaleString("en-US", { timeZone: "UTC"});

console.log("Real time:", localTime);