using System;

using DateTimeToStringWithSuffix;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(DateTime.UtcNow.ToString("d MMM"));  // 1 May

        Console.WriteLine(DateTime.UtcNow.ToStringWithSuffix("d MMM")); // 1st May

        // Console.WriteLine(DateTime.UtcNow.ToStringWithSuffix("MMM")); // ArgumentException - missing "d" or "dd"

    }

}