using System;

using System.Globalization;

​

namespace ConsoleApplication9

{

    public class Program

    {   

        public static void Main(string[] args)

        {

                string s = "Jul 28 00:00";

                DateTime dt;

                if(DateTime.TryParseExact(s, "MMM dd HH:mm", CultureInfo.InvariantCulture,

                                          DateTimeStyles.None, out dt))

                {

                    Console.WriteLine(dt.ToString("yyyy-MM-dd tt 00:00", CultureInfo.InvariantCulture));

                }

        }

    }

}