Format Date as "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"

I need to format a date as yyyy-MM-dd'T'HH:mm:ss.SSS'Z' as specified by Parse's REST API for Facebook. I was wondering what the most lightweight solution to this would be.

Call the toISOString() method:

var dt = new Date("30 July 2010 15:05 UTC");
document.write(dt.toISOString());

// Output:
//  2010-07-30T15:05:00.000Z

toISOString() will return current UTC time only not the current local time. If you want to get the current local time in yyyy-MM-ddTHH:mm:ss.SSSZ format then you should get the current time using following two methods

Method 1:

console.log(new Date(new Date().toString().split('GMT')[0]+' UTC').toISOString());

Method 2:

console.log(new Date(new Date().getTime() - new Date().getTimezoneOffset() * 60000).toISOString());

function converToLocalTime(serverDate) {

    var dt = new Date(Date.parse(serverDate));
    var localDate = dt;
    
    var gmt = localDate;
        var min = gmt.getTime() / 1000 / 60; // convert gmt date to minutes
        var localNow = new Date().getTimezoneOffset(); // get the timezone
        // offset in minutes
        var localTime = min - localNow; // get the local time

    var dateStr = new Date(localTime * 1000 * 60);
    // dateStr = dateStr.toISOString("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"); // this will return as just the server date format i.e., yyyy-MM-dd'T'HH:mm:ss.SSS'Z'
    dateStr = dateStr.toString("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
    return dateStr;
}

Add another option, maybe not the most lightweight.

dayjs.extend(dayjs_plugin_customParseFormat)
console.log(dayjs('2018-09-06 17:00:00').format( 'YYYY-MM-DDTHH:mm:ss.000ZZ'))

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dayjs.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/plugin/customParseFormat.js"></script>

Node.js

const offsetInMinutes = 2 * 60 ; //Romanian
const todaysDate = new Date(new Date().getTime() + offsetInMinutes * 60000).toISOString();

You can use javax.xml.bind.DatatypeConverter class

DatatypeConverter.printDateTime & DatatypeConverter.parseDateTime