javascript toISOString() ignores timezone offset [duplicate]

I am trying to convert Twitter datetime to a local iso-string (for prettyDate) now for 2 days. I'm just not getting the local time right..

im using the following function:

function getLocalISOTime(twDate) {
    var d = new Date(twDate);
    var utcd = Date.UTC(d.getFullYear(), d.getMonth(), d.getDate(), d.getHours(),
        d.getMinutes(), d.getSeconds(), d.getMilliseconds());

    // obtain local UTC offset and convert to msec
    localOffset = d.getTimezoneOffset() * 60000;
    var newdate = new Date(utcd + localOffset);
    return newdate.toISOString().replace(".000", "");
}

in newdate everything is ok but the toISOString() throws it back to the original time again... Can anybody help me get the local time in iso from the Twitterdate formatted as: Thu, 31 May 2012 08:33:41 +0000

Solution 1:

moment.js is great but sometimes you don't want to pull a large number of dependencies for simple things.

The following works as well:

    var tzoffset = (new Date()).getTimezoneOffset() * 60000; //offset in milliseconds
    var localISOTime = (new Date(Date.now() - tzoffset)).toISOString().slice(0, -1);
    
    console.log(localISOTime)  // => '2015-01-26T06:40:36.181'

The slice(0, -1) gets rid of the trailing Z which represents Zulu timezone and can be replaced by your own.

Solution 2:

My solution without using moment is to convert it to a timestamp, add the timezone offset, then convert back to a date object, and then run the toISOString()

var date = new Date(); // Or the date you'd like converted.
var isoDateTime = new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString();