var img1 = new Image(); img1.src = 'images/spinner.gif';
    function nextMonth() {
      CallBack1.Callback(Calendar1.FormatDate(Calendar1.GetNextVisibleDate(), "yyyy-M-d")); 
    }
    
    function prevMonth() {
      CallBack1.Callback(Calendar1.FormatDate(Calendar1.GetPrevVisibleDate(), "yyyy-M-d")); 
    }