using System;

using System.Globalization;

using System.Threading.Tasks;

using System.Collections.Generic;

using System.Linq;

​

​

public class Program

{

    public static DateTime ParseDate(string input)

    {

        DateTime result;

        if (DateTime.TryParseExact(input, "yyyy-MM-dd", CultureInfo.CurrentCulture, DateTimeStyles.None, out result)) return result;

        if (DateTime.TryParseExact(input, "dd-MM-yyyy", CultureInfo.CurrentCulture, DateTimeStyles.None, out result)) return result;

        throw new FormatException();

    }

    public static void Main()

    {

        string[] tests = new string[] { "2018-06-29", "29-06-2018","Invalid" };

        foreach (var t in tests)

        {

            var result = ParseDate(t);

            Console.WriteLine( "Year: {0}  Month: {1}  Day: {2}", result.Year, result.Month, result.Day );

        }

    }

}