using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Text.RegularExpressions;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        DateTime dt = new DateTime();

        string userInput;

        do

        {

            Console.Write("Please enter your birth date in YYYY.MM.DD format: ");

            userInput = Console.ReadLine();

        }

        while (!DateTime.TryParseExact(userInput, "yyyy.MM.dd",

                                       CultureInfo.InvariantCulture,

                                       DateTimeStyles.None,

                                       out dt));

        Console.WriteLine("You were born on:  \"{0}\"\n", dt.ToString("yyyy.MMMM.dd"));

        Console.ReadLine();

    }

}