UTC Offset in Seconds to Date in Javascript-CodePudding

i've been working with an api that returns the time in an UTC offset like '7000' in seconds, im trying to pass to a date like '2020-01-01T01:56:40.000Z' or time like '1:12:03 PM'

i have tried this but returns a wrong date, as if i was giving it a value in ms


var utcSeconds = 7000;
var d = new Date(7000); 

console.log(d);  // 1970-01-01T00:00:07.000Z

All i've been able see online is the oposite proccedure or different procedure, hope you can help me, Thanks!

CodePudding user response：

One way to do this is to find a canonical IANA timezone that matches the UTC offset you get from the API. These look like 'Etc/GMT-9' and have a fixed UTC offset. (See List of tz database timezones)

Once we have this timezone we can use Date.toLocaleTimeString() to format the local time.

We can wrap all this up in a function formatLocalTime() that will display the time at that UTC offset.

function getIANATimezone(utcOffsetSeconds) {
    const utcOffsetHours = Math.abs(utcOffsetSeconds / 3600);
    const sign = (utcOffsetSeconds < 0 ) ? ' ': '-';
    return `Etc/GMT${sign}${utcOffsetHours}`;
}

function formatLocalTime(utcOffsetSeconds) {
    const timeZone = getIANATimezone(utcOffsetSeconds);
    return new Date().toLocaleTimeString('en-US', { timeZone });
}

const utcOffsets = [32400,-25200, 0, 3600];
console.log('UTC Offset(s)\tLocal time')
for(let utcOffset of utcOffsets) {
    console.log(utcOffset   '', '\t\t', formatLocalTime(utcOffset))
}

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