using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

​

        DateTime result;

        CultureInfo provider = CultureInfo.InvariantCulture;

        string dateString = "20201220 2:30:55";

        string format = "yyyyMMdd h:mm:ss";

        result = DateTime.ParseExact(dateString, format, provider);

        Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());

    }

}