Display end dates based on default duration

gistfile1.html

<!-- inside cart.items for loop -->
                    {% for p in item.properties %}
                        {% unless p.last == blank %}
                            <span class="date" data-date="{{ p.last | date:'%c' }}" data-duration="{{ item.variant.metafields.bookthatapp.duration }}">{{ p.first | replace: 'booking-start', 'Date' | replace: 'booking-time', 'Time' }}:&nbsp{% if p.last contains '/uploads/' %}{{ p.last | split: '/' | last }}{% else %}{{ p.last }}{% endif %}</span><br />
                        {% endunless %}
                    {% endfor %}


<script type="text/javascript">// at the bottom of cart.liquid
    pad = function(n) {
        return ('0' + n).slice(-2);
    }

  jQuery(document).ready(function($) {
    $('span.date').each(function() {
        var start = new Date($(this).attr('data-date')),
            days = parseInt($(this).attr('data-duration'), 10)/1440,
            finish = new Date();
        
        finish.setDate(start.getDate() + days);
        var text = ' - ' + pad(finish.getMonth() + 1) + "/" + pad(finish.getDate()) + "/" + finish.getFullYear()
        
        $(this).append($('<span>').text(text));
    })
  })
</script>