Prototype a method onto the Date object that returns a UTCDateTime string.

getUTCDateTime.js

Date.prototype.getUTCDateTime = function() {
    var zf = function(num) {
            return ((num + 100) + '').substr(1);
        };

	return [
		this.getUTCFullYear(),
		'-',
		zf(this.getUTCMonth() + 1),
		'-',
		zf(this.getUTCDate()),
		'T',
		zf(this.getUTCHours()),
		':',
		zf(this.getUTCMinutes()),
		':',
		zf(this.getUTCSeconds()),
		'Z'
	].join('');
};