format json date to mm/dd/yy format before displaying in a jquery datatable

For dot.net and javascript, you can just use like @David Sopko

 {
                "data": "Date", "type": "date ",
                "render": function (value) {
                    if (value === null) return "";
                    var pattern = /Date\(([^)]+)\)/;//date format from server side
                    var results = pattern.exec(value);
                    var dt = new Date(parseFloat(results[1]));

                    return dt.getDate() + "." + (dt.getMonth() + 1) + "." + dt.getFullYear();
                }, "autoWidth": true
            },

For a nullable date time, DateTime?, you will want to use a different rendering function:

        $('#userData').DataTable({
        columns: [
            { "data": "userId"},
            {"data": "userCreated",
             "type": "date ",
             "render":function (value) {
                 if (value === null) return "";

                  var pattern = /Date\(([^)]+)\)/;
                  var results = pattern.exec(value);
                  var dt = new Date(parseFloat(results[1]));

                  return (dt.getMonth() + 1) + "/" + dt.getDate() + "/" + dt.getFullYear();}
            }
        ]};

You can use "render" property to format your column display http://datatables.net/reference/option/columns.render#function.

For example:

{
    "data": "createdTime",
    "render": function (data) {
        var date = new Date(data);
        var month = date.getMonth() + 1;
        return (month.toString().length > 1 ? month : "0" + month) + "/" + date.getDate() + "/" + date.getFullYear();
    }
}

i have created demo using moment js and use of render function to convert json data into required format.

jsfiddle demo

also find code below:

testdata = [{
    "id": "58",
        "country_code": "UK",
        "title": "Legal Director",
        "pubdate": "1422454697373",
        "url": "http://..."
}, {
    "id": "59",
        "country_code": "UK",
        "title": "Solutions Architect,",
        "pubdate": "1422454697373",
        "url": "http://..."
}];

$('#test').dataTable({
    "aaData": testdata,
        "aoColumns": [{
        "mDataProp": "id"
    }, {
        "mDataProp": "country_code"
    }, {
        "mDataProp": "title"
    }, {
        "mDataProp": "pubdate"
    }, {
        "mDataProp": "url"
    }],
        "columnDefs": [{
        "targets": 3,
            "data": "pubdate",
            "render": function (data, type, full, meta) {
                console.log('hi...');
            console.log(data);
                console.log(type);
                console.log(full);
                console.log(meta);
            return moment.utc(data, "x").toISOString();
        }
    }]
});