The getDay() method returns a number to indicate the day in week (0=Sun, 1=Mon, ... 6=Sat). Use getDate() to return a number for the day in month:
var day = convertedStartDate.getDate();
If you like, you can try to add a custom format function to the prototype of the Date object:
Date.prototype.formatMMDDYYYY = function(){
return (this.getMonth() + 1) +
"/" + this.getDate() +
"/" + this.getFullYear();
}
After doing this, you can call formatMMDDYYY() on any instance of the Date object. Of course, this is just a very specific example, and if you really need it, you can write a generic formatting function that would do this based on a formatting string, kinda like java's SimpleDateeFormat (http://java.sun.com/j2se/1.4.2/docs/api/java/text/SimpleDateFormat.html)
(tangent: the Date object always confuses me... getYear() vs getFullYear(), getDate() vs getDay(), getDate() ranges from 1..31, but getMonth() from 0..11
It's a mess, and I always need to take a peek. http://www.w3schools.com/jsref/jsref_obj_date.asp)