getTimezoneOffset() returns 0

I am trying to write a service that returns the local time offset from UTC. I simply create a new Date() object and run the getTimezoneOffset() on this object. I verified that the date object is indeed my local time, but the getTimezoneOffset() is returning 0. How can I get the offset from UTC?

var date = new Date(); // this is returning my local date/time
var localOffset = date.getTimezoneOffset(); //this is returning 0