select date angularjs directive (using: <div selectdate yu-model="user.birthdate_on"></div>)

gistfile1.coffee

.directive "selectdate", ($translate)->
  restrict: 'A'
  scope:
    yuModel: '='
  controller: ($scope, $element) ->
    $scope.months = [
      {value: 1, name: 'jan'},
      {value: 2, name: 'feb'},
      {value: 3, name: 'mar'},
      {value: 4, name: 'apr'},
      {value: 5, name: 'may'},
      {value: 6, name: 'jun'},
      {value: 7, name: 'jul'},
      {value: 8, name: 'aug'},
      {value: 9, name: 'sep'},
      {value: 10, name: 'oct'},
      {value: 11, name: 'nov'},
      {value: 12, name: 'dec'}
    ]
  link: ($scope, element, attrs, ctrls) ->
    now = new Date($scope.yuModel)
    [$scope.dateDay, $scope.dateMonth, $scope.dateYear] = [now.getDay(), now.getMonth(), now.getFullYear()]

    $scope.dateChanged = ->
      @yuModel = "#{$scope.dateYear}-#{$scope.dateMonth}-#{$scope.dateDay}"
    $scope.$watch 'dateDay',   (newValue, oldValue) -> $scope.dateChanged()
    $scope.$watch 'dateMonth', (newValue, oldValue) -> $scope.dateChanged()
    $scope.$watch 'dateYear',  (newValue, oldValue) -> $scope.dateChanged()

  template: """
        <div class="date">
          <div class="custom-select day">
            <select ng-model="dateDay" ng-options="day for day in [] | range:1:31">
              <option value="" ng-if="false"></option>
            </select>
          </div>
          <div class="custom-select month">
            <select ng-model="dateMonth" ng-options="m.value as m.name|translate for m in months">
              <option value="" ng-if="false"></option>
            </select>
          </div>
          <div class="custom-select year">
            <select ng-model="dateYear" ng-options="year for year in [] | range:1930:2000">
              <option value="" ng-if="false"></option>
            </select>
          </div>
        </div>
      """
  replace: true

I am pro-beginner in angular and I like this. But if you use rails, you can render this 3 select via standart
form date helper and bind some var of scope to it, dont you think?
I dont know all context, but why you assing date in string format to this.yuModel, is it for view or it internal state of some model?