Нужно поменять формат даты

var nowTemp = new Date(); 
var now = new Date(nowTemp.getFullYear(), nowTemp.getMonth(), nowTemp.getDate(), 0, 0, 0, 0); 
 
var checkin = $('#pick-up-date').datepicker({ 
  onRender: function(date) { 
    return date.valueOf() < now.valueOf() ? 'disabled' : ''; 
  } 
}).on('changeDate', function(ev) { 
  if (ev.date.valueOf() > checkout.date.valueOf()) { 
    var newDate = new Date(ev.date) 
    newDate.setDate(newDate.getDate() + 1); 
    checkout.setValue(newDate); 
  } 
  checkin.hide(); 
  $('#drop-off-date')[0].focus(); 
}).data('datepicker'); 
var checkout = $('#drop-off-date').datepicker({ 
  onRender: function(date) { 
    return date.valueOf() <= checkin.date.valueOf() ? 'disabled' : ''; 
  } 
}).on('changeDate', function(ev) { 
  checkout.hide(); 
}).data('datepicker');

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<script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script>