I'm pretty sure that this is the date in milliseconds.
I had the same problem a while ago and solved it using the following code. However, I wanted the MMM/DD/YYYY format, so you'll have to change the string a bit.
function convertDate(date) {
var months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
return months[date.getUTCMonth()] + ' ' + date.getUTCDate() + ' ' + date.getUTCFullYear();
}
console.log(convertDate(new Date(1430953200000));