Can I use ng-model with isolated scope?

I am creating simple ui-datetime directive. It splits javascript Date object into _date, _hours and _minutes parts. _date uses jquery ui datepicker, _hours and _minutes - number inputs.

angular.module("ExperimentsModule", [])
    .directive("uiDatetime", function () {
    return {
        restrict: 'EA',
        replace: true,
        template: '<div class="ui-datetime">' +
            '<input type="text" ng-model="_date" class="date">' +
            '<input type="number" ng-model="_hours" min="0" max="23" class="hours">' +
            '<input type="number" ng-model="_minutes" min="0" max="59" class="minutes">' +
            '<br />Child datetime1: {{datetime1}}' +
            '</div>',
        require: 'ngModel',
        scope: true,
        link: function (scope, element, attrs, ngModelCtrl) {
            var elDate = element.find('input.date');

            ngModelCtrl.$render = function () {
                var date = new Date(ngModelCtrl.$viewValue);
                var fillNull = function (num) {
                    if (num < 10) return '0' + num;
                    return num;
                };
                scope._date = fillNull(date.getDate()) + '.' + fillNull(date.getMonth() + 1) + '.' + date.getFullYear();
                scope._hours = date.getHours();
                scope._minutes = date.getMinutes();
            };

            elDate.datepicker({
                dateFormat: 'dd.mm.yy',
                onSelect: function (value, picker) {
                    scope._date = value;
                    scope.$apply();
                }
            });

            var watchExpr = function () {
                var res = scope.$eval('_date').split('.');
                if (res.length == 3) return new Date(res[2], res[1] - 1, res[0], scope.$eval('_hours'), scope.$eval('_minutes'));
                return 0;
            };
            scope.$watch(watchExpr, function (newValue) {
                ngModelCtrl.$setViewValue(newValue);
            }, true);
        }
    };
});

function TestController($scope) {
    $scope.datetime1 = new Date();
}

jsfiddle

On github: https://github.com/andreev-artem/angular_experiments/tree/master/ui-datetime

As far as I understand - best practice when you create a new component is to use isolated scope.

When I tried to use isolated scope - nothing works. ngModel.$viewValue === undefined.

When I tried to use new scope (my example, not so good variant imho) - ngModel uses value on newly created scope.

Of course I can create directive with isolated scope and work with ngModel value through "=expression" (example). But I think that working with ngModelController is a better practice.

My questions:

1. Can I use ngModelController with isolated scope?
2. If it is not possible which solution is better for creating such component?