Adding days to a date in C#
We can add days to a date like below.
C# will take care of month and year when you add the days since it adheres to universal date and time rules. 

using System;

namespace forgetCode
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine("Enter year in the format dd-mm-yyyy");
            DateTime dt = Convert.ToDateTime(Console.ReadLine());

            Console.WriteLine("Enter the days to add :");
            int days = Convert.ToInt32(Console.ReadLine());

            DateTime newDate = dt.AddDays(days);
            Console.WriteLine(newDate.ToShortDateString());
       
            
        }

    }
}


Output:
Enter year in the format dd-mm-yyyy
25-12-2012
Enter the days to add :
7
01-01-2013

..