using System;

public class Program

{

    public static void Main()

    {

            DateTime date1 = new DateTime(2000, 3, 05);

​

            System.Console.WriteLine(CalculateAge(date1));

    }

        public static int CalculateAge(DateTime birthDate)

        {

            var now = new DateTime(2018, 3, 05);  

​

            var age = now.Year - birthDate.Year;

​

            if (now.Month < birthDate.Month || 

                (now.Month == birthDate.Month && 

                 now.Day < birthDate.Day))

            {

                age--;

            }

​

            return age;

        }

}