When a Moment object is used for ng-model instead of a Date object, the timezone information set on the moment is lost.
The code is using a moment's underlying Date object which doesn't contain any timezone information.
If supporting moment.js, I think it is important to retain timezone information or at least call out in the documentation that timezone information will be lost.
http://plnkr.co/edit/BqBS59XvZlH5KMbulTgQ?p=preview