function _init(element, userOptions){
            targetElement = $(element);

            var options = $.extend({
                "field"      : targetElement.get(0),
                "defaultDate": targetElement.val(),
                "setDefaultDate": true,
                "format": "YYYY-MM-DD"
            }, userOptions);

            if (!targetElement.data("pickaday")){
                var pikaday = new Pikaday(options);
                targetElement.data("pickaday", pikaday);
            }

            targetElement.next(".btn-calendar").on("click", function(){
                targetElement.data("pickaday").show();
            });

            if(targetElement.val().length > 0 && options.silent !== true){
                _setDate(targetElement.val());
            }
        }
yobi.ui.Calendar

@requires Pikaday.js (https://github.com/dbushell/Pikaday/)