JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/knockout.mapping/2.3.5/knockout.mapping.js"></script>
<table>
    <tbody data-bind="foreach: items">
        <tr class="gv">
            <td data-bind="text: id"></td>
            <td data-bind="text: number"></td>
            <td data-bind="text: unixTs"></td>
        </tr>
    </tbody>
</table>

CSS

td { border: 1px solid gray; padding: 1em; }

JavaScript

var data = {
    items: [{id: 1,number: 42,date_time: 1375948769449},
            {id: 2,number: 106,date_time: 1375948769349}]
};

var ItemViewModel = function (data) {
    var self = this;
    ko.mapping.fromJS(data, {}, self);
    this.unixTs = ko.computed(function () {
        var date = new Date(self.date_time());
        var hours = date.getHours();
        var minutes = date.getMinutes();
        var seconds = date.getSeconds();
        return hours + ':' + minutes + ':' + seconds;
    });
};

var mapping = {
    'items': {
        create: function (item) {
            return new ItemViewModel(item.data);
        }
    }
};

var viewModel = ko.mapping.fromJS(data, mapping, {});

ko.applyBindings(viewModel);