I have guess cuz I dont so know javascript or jquery syntax.
But can you try code below,bro.
<script type="text/javascript">
var dateString = data.NewsByIdResult[i].ModifiedDate.substr(6);
var currentTime = new Date(parseInt(dateString));
var monthNumber = currentTime.getMonth() + 1;
var day = currentTime.getDate();
var year = currentTime.getFullYear();
var months = [ "Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec" ];
var monthName = months[monthNumber];
var ampm = (currentTime.getHours() >= 12) ? 'PM' : 'AM';
var times = (currentTime.getHours() >= 12) ? currentTime.getHours()-12 + ':' + currentTime.getMinutes() + ' ' + ampm : currentTime.getHours() + ':' + currentTime.getMinutes() + ' ' + ampm;
var yourWantOutput = monthName + ' ' + day + ' ' + year + ' ' + times;
alert(yourWantOutput);
</script>