using datepicker on selecting date value not binding to model Angular js

i am using datepicker but here facing problem regarding model value not binding to model when i select date its nothing happen, any one can tell me where i am doing wrong must be appreciated. here i am sending my code.Showing date picker just problem after selecting date value not not binding to ng-model="user.dob".

signUpview.html

<div class="col-md-6">
<label for="datepicker" class="col-lg-5 form-label">Date Of Birth:</label>
    <div class="col-lg-7">
 <input type="text" class="form-control dateBirth" ng-model="user.dob" id="datepicker" name="datepicker" datepicker placeholder="Date Of Birth" required/>
 <div class="error" ng-show="newUser_form.datepicker.$dirty && newUser_form.datepicker.$invalid">
 <small class="error errorFields" ng-show="newUser_form.datepicker.$error.required"> Date is required.</small>
                                </div>
                            </div>
</div>

datepickerDirective.js

app.directive('datepicker', function() {
    var linker = function(scope, element, attrs) {
        element.datepicker().on('changeDate', function(){
            console.log(scope);

            $(".datepicker").hide();
        });
    }
    return {
        require: 'ngModel',
        restrict: 'A',
        link: linker
    }
});