title: how to create an angular datepicker directive that uses ng-model
body: <p>I have created an angular directive for my jQuery UI datepicker. The problem is that the directive doesn't update the input's ng-model when a date is selected. Any idea why?</p>
  
  <p><a href="http://jsbin.com/ufoqan/1/edit" rel="noreferrer">http://jsbin.com/ufoqan/1/edit</a></p>