Add these two script file in your page
if you don't have these Script plugin then go through these link and download it first.
@
download[
^]
And try like this it will work 100%
<script language="javascript" type="text/javascript" src="~/Scripts/date.js"></script>
<script language="javascript" type="text/javascript" src="~/Scripts/time.js"></script>
var today = Date.today();
$('#EndDateConsumption').val(today.toString("MM/dd/yyyy"));
var $startDate = $('#EndDateConsumption');
var $endDate = $('#StartDateConsumption');
var dStartDate = Date.parseExact($startDate.val(), "MM/dd/yyyy");
var prevDate = dStartDate.add(-1).months();
$endDate.val(prevDate.toString("MM/dd/yyyy"));
Enjoy :)