getMonth in javascript gives previous month

Presuming you use your variable

var d1 = new Date("Sun Jul 7 00:00:00 EDT 2013");

Month requires a +1 to be accurate, it starts counting at 0

d1.getMonth() + 1 // month 

In contrast.... these methods DON'T need a plus 1

d1.getSeconds()   // seconds 
d1.getMinutes()   // minutes 
d1.getDate()      // date    

And notice it is .getDate() NOT .getDay()

d1.getDay()       // day of the week as a 

Hope this helps

I suspect these methods lack consistency for historical reasons

getMonth() function is zero indexed based. You need to do d1.getMonth() + 1

Recently I used Moment.js library and never looked back. Try it!

Because getmonth() start from 0. You may want to have d1.getMonth() + 1 to achieve what you want.