using System;

using System.Linq;

using System.Text.RegularExpressions;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        // Check your first date

        var a = FormatDate("6/19/2014 12:21:15 AM"); // yields "6/19/2014 12:21:15 AM"

        Console.WriteLine(a);

        // Check the other date

        var b = FormatDate("13-10-2014 16:41:15");   // yields "10/13/2014 4:41:15 PM"

        Console.WriteLine(b);

    }

    public static DateTime? FormatDate(string d)

    {

            // DateTime variable to store your value

            DateTime date;

            // Attempt to parse your Date using either of the formats provided

            if(DateTime.TryParseExact(d, new []{ "M/d/yyyy hh:mm:ss tt", "d-M-yyyy HH:mm:ss" },null, DateTimeStyles.None, out date))

            {

                 // Your date was able to be read properly and will be stored in the date variable

                 return date;

            }

            else

            {

                 // Your date was not in either of the formats provided, consider throwing an error

                 return null;

            }

    }

}