Hi Firuz,
Refer the below code.
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
$(function () {
var th = $('[title="Calendar"]').find('tr').eq(2).find('th');
$(th)[0].innerHTML = 'Вс'; // SunDay
$(th)[1].innerHTML = 'Пн'; // MonDay
$(th)[2].innerHTML = 'Tu'; // TuesDay
$(th)[3].innerHTML = 'We'; // WednesDay
$(th)[4].innerHTML = 'Th'; // ThursDay
$(th)[5].innerHTML = 'Fr'; // Friday
$(th)[6].innerHTML = 'Sa'; // Saturday
});
</script>