Fullcalendar - Uncaught TypeError: Cannot read property 'hasTime' of undefined

        var Calendar = jQuery('#calendar');
        var Months = jQuery('#months');
        var event_title = jQuery('#event_title');
        var event_start = jQuery('#event_start');
        var event_end = jQuery('#event_end');
        var event_description = jQuery('#description');
        var form = jQuery('#dialog-form');
      
        Calendar.fullCalendar({
        aspectRatio: 1.5,
        fixedWeekCount: false,
        showNonCurrentDates: false,
        eventLimit: true,   
    header: {
        left: "",
        center: "title",
        right: "prev today next" 
        },
    
events: "ajax.php",  

    //клик по дню
    dayClick: function(date,jsEvent,view){

    var clickDate = date.format('YYYY-MM-DD');
    console.log(clickDate);
    form.dialog({
    modal: true,
    width: '30%',
    title: "Добавление события",
    buttons: [{
    id: 'add',
    text: 'Добавить',
    click: function() {
        
        $.ajax({
            type: "POST",
            url: "ajax.php",
            data: {

               title: event_title.val(),
               start: event_start.val(),
               end: event_end.val()
            }
                     //начало проблемы 
            success: function(){
                Calendar.fullCalendar('renderEvent', {
                    title: event_title.val(),
                    start: event_start.val(),
                    end: event_end.val(),
                              allDay: false
                });
            }
        });
        emptyForm();
    }
},
    {   id: 'edit',
        text: 'Изменить',
        click: function() {
           
        }
    },
    {   id: 'cancel',
        text: 'Отмена',
        click: function() { 
            $(this).dialog('close');
            emptyForm();
        }
    },
    {   id: 'delete',
        text: 'Удалить',
        click: function() { 
            
        },
        disabled: true
    }]
    });
    //календарь для выбора начала и конца события в модалке
    event_start.val(clickDate);
    event_end.val(clickDate);
    $('.datepicker').datepicker({ dateFormat: 'yy-mm-dd' });
    formOpen('add');
},
    //клик по событию
    eventClick: function (event, jsEvent, view) {
        $("#eventInfo").html(event.description);
        $("#eventContent").dialog({
            modal: true,
            width: '30%',
            title: event.title,
            closeText: "",
            buttons: [{text: "Закрыть",
            click: function() { $(this).dialog("close")}}]
            }); 
            },
      
    // Выпадающий список с месяцами 
    eventAfterAllRender: function(){
            var date = Calendar.fullCalendar('getDate');
            var month = date.month();
            month ++;
            Months.val(month);
            var $header = Calendar.find('.fc-left');
            if (!(Calendar.find("#months").length > 0)) {
                $header.prepend(Months);}
                }                   
                });                 
    Months.off('change').change(function(){
            var $select = jQuery(this);
            var newMonth = parseInt($select.val());
            newMonth--;
            var date = Calendar.fullCalendar('getDate');
            date.month(newMonth);
            Calendar.fullCalendar('gotoDate', date);
            });
            
        
    

    // функция очистки модалки
    function emptyForm() {
    event_title.val("");
    event_start.val("");
    event_end.val("");
    <!-- event_description.val(""); -->
    }
    //режимы открытия модалки
    function formOpen(mode) {
    if(mode == 'add') {
        $('#add').show();
        $('#edit').hide();
        $("#delete").button("option", "disabled", true);
    }
    else if(mode == 'edit') {
        $('#edit').show();
        $('#add').hide();
        $("#delete").button("option", "disabled", false);
    }
    form.dialog('open');
    }



> css

body{
background: #f7f7f7 !important;
}
.menu-event{
    float: right;
    padding: 10px;
    flex-basis: 290px;
    word-wrap: break-word;
    border-radius: 10px;
    background: white;
    display: inline-block;
    flex: 1 1 50px;
    width: 20%;
    margin-right: 35px;
    height: 710px;
}
.box {
    border-radius:10px;
    flex-wrap: wrap;
    justify-content: space-around;
    width:70%;
    display: inline-block;
    position:relative;
  }
  
  .calendar{
    border-radius:10px;
    padding: 7px;
    background: white;
    display: inline-block;
    flex: 1 1 50px;
   width: 100%;
  
  }
  .month{
  font-size: 12px;
  padding:10px;
  border:1px solid #ddd;
  border-radius:10px;
  }
  .month:hover{
  cursor: pointer;}
a{text-decoration: underline;} 
.fc-day-grid-event > .fc-content{
white-space: overflow;
text-overflow: ellipsis;
font-size:10px;
max-height:45px;
padding:1px;
}
select{text-align-last: center;}
th.fc-sat, th.fc-sun, td.fc-sat, td.fc-sun{ color:red;}
.fc-basic-view td.fc-day-number{padding:1px 5px 0 0;}
td.fc-today {color:white;}
.fc-day.fc-today {
    position: relative;
    right: 1px;
    top:0px;
}

.fc-today{
background: rgba(255,220,40,.15);
}

.fc-day.fc-today::before,
.fc-day.fc-today::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    border-color: transparent;
    border-style: solid;
}   

.fc-day.fc-today::before {
   width:20px;
    height:11px;
}

.fc-day.fc-today::after {
    border-radius:  50% 0 0 50%;
    width:20px;
    height:11px;
    background-color: #E30611;
}

.fc-content:hover {
background-color: rgba(185, 233, 255, 1);
cursor: pointer;
  position: relative;
  white-space: normal;
}

.fc-head{
background: #F0F8FF;
}

div.fc-more-popover > .fc-widget-content > .fc-event-container >.fc-day-grid-event > .fc-content{
white-space: normal;
}
.fc-ltr .fc-basic-view .fc-day-number {
background: rgba(240, 248, 255, 0.4);
}
.fc td{
border: 2px solid #DCDCDC;
}


.btn{
  font-size: 16px;
  padding:10px;
  border:1px solid #ddd;
  border-radius:10px;
  background: white;
}
> html

<!DOCTYPE html>
<html lang="ru">
<head>
    <meta charset="UTF-8">
    <title>Календарь событий</title> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/fullcalendar/2.6.0/fullcalendar.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/fullcalendar/2.6.0/fullcalendar.min.css"rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.11.2/moment.min.js"></script>
<script src="http://code.jquery.com/ui/1.11.3/jquery-ui.min.js"></script>
</head>
<body>

<div class="box">
    <select class="month" id="months" tabindex="0">
        <option selected disabled>Выбрать месяц</option>
        <option value="1">Январь</option>
        <option value="2">Февраль</option>
        <option value="3">Март</option>
        <option value="4">Апрель</option>
        <option value="5">Май</option>
        <option value="6">Июнь</option>
        <option value="7">Июль</option>
        <option value="8">Август</option>
        <option value="9">Сентябрь</option>
        <option value="10">Октябрь</option>
        <option value="11">Ноябрь</option>
        <option value="12">Декабрь</option>
    </select>

        <div id="calendar" class="calendar"></div>
        <div id="eventContent">
        <div id="eventInfo">
        </div>
    </div>
    </div>
    
    
<div id="dialog-form" style="display:none" title="Событие">
    <form>
        <p><label for="event_title">Заголовок события</label>
        <input type="text" id="event_title" value=""></p>
        <p><label for="event_start">Начало</label>
        <input type="text" value="" class="datepicker" id="event_start"/></p>
        <p><label for="event_end">Конец</label>
        <input type="text" value="" class="datepicker" id="event_end"/></p>
        </form>
</div>



</body>
</html>