Как сосчитать срок аренды в корзине в Tilda

<style>
    .redtext{ color:#ff0000 !important;font-weight: 600;}
    .blkbtn{opacity: 0.2; pointer-events: none;  }
    .t706 .t-input-group_da { width: 48%}
    @media screen and (max-width: 450px){
    .t706 .t-input-group_da { width:auto;float:none!important;}
    }
    .t706 .t-input-group_da:nth-child(2) { float: left}   
    .t706 .t-input-group_da:nth-child(3) { float: right}
    .t706 .t-input-group_ph {clear: both}
    .pastDay{
    opacity: 0.2;
    pointer-events: none;
}
    .pastDay td:before ,  td.pastDay:before{
    content:'';
    position:absolute;
    display:block;
    width:auto;
    height:auto;
    left:0;
    top:0;
    right:0;
    bottom:0;
    background: rgba(0,0,0,0) url(https://static.tildacdn.com/tild3234-3362-4361-b061-643132376234/cancel_1.svg) no-repeat;
    background-size:100% 100%; 
}
.t706__product-plusminus {
    display: block !important;
    opacity: 0;
    pointer-events: none;
}
</style>

<script>
$(document).ready(function(){
$('.t706 .t-form__submit').addClass('blkbtn');  
var date = new Date();
Month = date.getMonth()+1;
Year = date.getFullYear();
  $("form").on('DOMSubtreeModified', ".t-input-block_inited-date-picker", function() {
    $('.today').prevAll('tbody tr>td').addClass('pastDay');
    $('.today').parent('tr').prevAll('tr').addClass('pastDay');
     var picM = $('select.dp-select-month option:selected').val();
     var picD = $('select.dp-select-year option:selected').val();
     if (picM<Month && picD<=Year || picD<Year ){
         $('.cal-month tr').addClass('pastDay');
     };
  });
function checktime(){
setTimeout(function(){
    //Получаем значение дат
 var dt1 = $("input[name='datestart']").val();
 var dt2 = $("input[name='dateend']").val();
 //Приводим даты к нужному формату
 var arr1 = dt1.split('-');
 var arr2 = dt2.split('-');
 var novdt1 = arr1[1]+"/"+arr1[0]+"/"+arr1[2];
 var novdt2 = arr2[1]+"/"+arr2[0]+"/"+arr2[2];
 var datestart = new Date(novdt1);
 var dateend = new Date(novdt2);
//Вычисляем разницу между датами
 var days = (dateend-datestart)/86400000;
if (days>0&& !$('.date-picker').is(':visible')){
    $('.t-input-group_tx .t-text').removeClass('redtext').text('Срок аренды: '+days+' дн.');
    $("input[name='dateend']").removeClass('redtext');
    $('.t706 .t-form__submit').removeClass('blkbtn');
    $('.t706__product-quantity').html(days);
    if(days>5){$('.t706__product-quantity').html(days-1);};
    if(days>10){$('.t706__product-quantity').html(days-2);};
    if(days>20){$('.t706__product-quantity').html(days-5);};
    $('.t706__product-quantity').trigger("click");
    
    let qntInp = document.querySelector('input[name="tilda-tmp-cart-qnt"]');
    qntInp.blur();

};
if (days<1&&!$('.date-picker').is(':visible')){  
  $('.t-input-group_tx .t-text').addClass('redtext').text('Минамальная аренда 1 день');
  $("input[name='dateend']").addClass('redtext');
  $('.t706 .t-form__submit').addClass('blkbtn');
};
}, 300);       
};
$(document).on('click','.date-picker td , a[href^="#order"]',function(e){checktime()});
$('.t-datepicker__wrapper input').on("focusout",function(){checktime()}); 
});
</script>