How to convert a Date to UTC?

var date = new Date();
var now_utc = Date.UTC(date.getUTCFullYear(), date.getUTCMonth(),
                date.getUTCDate(), date.getUTCHours(),
                date.getUTCMinutes(), date.getUTCSeconds());

console.log(new Date(now_utc));
console.log(date.toISOString());