using System.Globalization;

using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter your birth date (if you are less than 16 year old you have to wait, if you are very old you can try to enter your birthdate in the dd/MM/yyyy format):");

        string dateString = Console.ReadLine();

        DateTime date;

        CultureInfo ci = (CultureInfo)CultureInfo.InvariantCulture.Clone();

        ci.Calendar.TwoDigitYearMax = DateTime.Now.Year - 16;

        if (!DateTime.TryParseExact(dateString, new string[]

        {

        "dd/MM/yyyy", "dd/MM/yy"

        }

​

        , ci, DateTimeStyles.None, out date))

        {

            throw new InvalidOperationException("Not a valid date");

        }

​

        Console.WriteLine(date.ToString("dd/MM/yyyy", CultureInfo.InvariantCulture));

    }

}