using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        DateTime dateValue;

        string dateString = "28/05/2015 15:55";

        if (DateTime.TryParse(dateString, CultureInfo.CreateSpecificCulture("en-US"), DateTimeStyles.None, out dateValue))

        {

            Console.WriteLine("Valid en-US date.");

        }

        else

        {

            Console.WriteLine("Not a valid en-US date.");

        }

        if (DateTime.TryParse(dateString, CultureInfo.CreateSpecificCulture("fr-FR"), DateTimeStyles.None, out dateValue))

        {

            Console.WriteLine("Valid fr-FR date.");

        }

        else

        {

            Console.WriteLine("Not a valid fr-FR date.");

        }

    }

}