using System;

public class Program

{

    public static void Main()

    {

        var dat = new DateTime(2015, 12, 31);

​

        //I am sure this will add 6 months

        dat = dat.AddMonths(6);

        Console.WriteLine(dat.ToString());

​

        //I am not sure what this does

        dat.AddMonths(6);

        Console.WriteLine(dat.ToString());  

    }

}