how to get the date of 7 days after a certain day in javascript

I am trying to find a solution about the subject. I am new to unity and english, so I think i should be more specific.

For example, I want to know the date of 7 days after yesterday. It could be any day, monday, tuesday…
Let’s say the base day is Aug. 29th. Then I need to get Sep. 5th.

Is there a solution in Javascript ?

You could just use DateTime:

var date : Date = System.DateTime().Now; 
             //or System.DateTime(2013, 8, 29)
var future : Date = date.AddDays(6); // -1 + 7 = 6 days
Debug.Log( future );
Debug.Log( future.ToString("dddd") ); //extract the weekday name

@edit

You can use the C# lib in this case because it’s implemented in UnityScript (actually it’s not JavaScript).