using System;

public class Program

{

    public static void Main()

    {

        var age = Calculate(new DateTime(2000,02,29));

        Console.WriteLine(age);

    }

    public static int Calculate(DateTime dateOfBirth)

    {

        var now = DateTime.Now;

​

        int age = now.Year - dateOfBirth.Year;

​

        if (now.Month < dateOfBirth.Month || (now.Month == dateOfBirth.Month && now.Day < dateOfBirth.Day))

            age--;

​

        return age;

    }

}