Subtract N Days From Current Date?

I have the following function that will subtract n number of days from todays date. The problem is that it always returns the the wrong calculate date. The month is wrong.

see if you can spot my mistake:

Code:

function returnDate(ndays){
var dayOfTheWeek = now.getDay();
now.setTime(now.getTime() - nDays * 24 * 60 * 60 * 1000);
alert(now); // returns current date
alet(now.getYear() + "/"+now.getMonth()+"/"+now.getDate()) // returns new calculated date
}