using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        var timeValue = "11:00:00 a.m.";

        DateTimeFormatInfo formatInfo = new()

        {

            AMDesignator = "a.m.",

            PMDesignator = "p.m."

        };

        var result = TimeOnly.ParseExact(timeValue, "hh:mm:ss tt", formatInfo);

        Console.WriteLine(result); // does not show tt ouput here but does in Visual Studio

    }

}