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

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:

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

Method 2:

document.write(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;
}