Добави 1000 дни към деня

using System;

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

            DateTime birthDay = DateTime.ParseExact(Console.ReadLine(), "dd-MM-yyyy",null);

            DateTime newDate = birthDay.AddDays(999);

            Console.WriteLine(newDate.ToString("dd.MM.yyyy",null));

        }
    }
}