using System;

using System.Globalization;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        string format = "dd MMMM yyyy HH:mm:ss";

        string date = "13th December 2019 12:54pm";

        DateTime dt;

        var result = DateTime.TryParseExact(date, format, CultureInfo.InvariantCulture, DateTimeStyles.AllowWhiteSpaces, out dt);

        Console.WriteLine(result);

        Console.WriteLine(dt);

        result = DateTime.TryParse(date, out dt);

            Console.WriteLine();

        Console.WriteLine(result);

        Console.WriteLine(dt);

    }

}