how to get the day from date picker using javascript

*****CODE START**********
var days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
var months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
var iMonthStart = [0,3,3,6,1,4,6,2,5,0,3,5,6,2];

var date = myDatePicker.selectedDate(); // Not sure what kind of datePicker you are using but you call the method that returns the selected date.
// 01234567
// yyyymmdd
var century = date.substring(0,2); // Century
var year = date.substring(2,2); //Year
var month = date.substring(4,2);
var day    = date.substring(6,2);

//Please refer to the algorithm described here: <a href="http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week">http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week</a>[<a href="http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week" target="_blank" title="New Window">^</a>]

var centuryForCalc = 2*(3-(century%4));
var yearForCalc = year/4;

//Test for leap year
var yearFull = date.substring(0,4);
var iModLeap = yearFull%4;
var monthTblVal = 0;
if(iModLeap == 0)
{
   // Leap Year
   if(month == 1)
   {
       monthTblVal = 6;
    }
    else if(month == 2)
    {
      monthTblVal = 2;
    }
    else
    {
      monthTblVal = iMonthStart[month]; 
    }
}
else
{
   monthTblVal = iMonthStart[month]; 
}

var iTotal = centuryForCalc + yearForCalc + year + monthTblVal + day;
var iDayIndex = iTotal%7;
var dayString = days[iDayIndex-1];
*********** CODE END **********

DateTime selected = datetimepicker.Value;
int day = selected.day;
string dayofweek = selected.dayofweek;