Bootstrap DatePicker Custom Binding

ko.bindingHandlers.datepicker = {
    init: function(element, valueAccessor, allBindingsAccessor) {
      //initialize datepicker with some optional options
      var options = allBindingsAccessor().datepickerOptions || {};
      $(element).datepicker(options);
      
      //when a user changes the date, update the view model
      ko.utils.registerEventHandler(element, "changeDate", function(event) {
             var value = valueAccessor();
             if (ko.isObservable(value)) {
                 value(event.date);
             }                
      });
    },
    update: function(element, valueAccessor)   {
        var widget = $(element).data("datepicker");
         //when the view model is updated, update the widget
        if (widget) {
            widget.date = ko.utils.unwrapObservable(valueAccessor());
            widget.setValue();            
        }
    }
};

var model = {
    test_date: ko.observable(new Date('2012/12/12'))
};

ko.applyBindings(model, $("#target")[0]);

gistfile1.txt

<div id='target'>
    <input data-bind='datepicker: test_date'/>
    
    <div data-bind="text: test_date"></div>
    
    <input data-bind='datepicker: test_date'/>
</div>