using System;

public class Program

{

    public static void Main()

    {

        FormataData("10/03/1980");

        FormataData("03/10/1980");

        FormataData("25/12/1980");

        FormataData("12/12/1980");

        FormataData("1980-03-10");

        FormataData("1980-12-25");

        FormataData("1980-12-11");

    }

    public static void FormataData(string dataString)

    {

        DateTime dataTime; 

        dataTime = DateTime.Parse(dataString, System.Globalization.CultureInfo.GetCultureInfo("pt-BR"));

        if(dataTime!=null)

        {

            Console.Write("data entrada: " + dataString);

            Console.Write(" virou datetime pt-br : " + dataTime.ToString("d", System.Globalization.CultureInfo.GetCultureInfo("pt-BR")));

            Console.WriteLine(" virou datetime en-us : " + dataTime.ToString("u", System.Globalization.CultureInfo.GetCultureInfo("en-US")).ToString().Split(' ')[0] );

        } 

        else

        {

            Console.WriteLine("data nao reconhecida : " + dataString);

        }

    }

}

​

​