using System;

using NodaTime;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(ConvertToUSCentral());

    }

        public static string ConvertToUSCentral(DateTime? dateTimeParam = null)

        {

            DateTime dateTime = new DateTime();

             if (dateTimeParam.HasValue  == true)

            {

                dateTime = (DateTime)dateTimeParam;

            }

            else

            {

                dateTime = DateTime.UtcNow;

            }

             var timeZone = DateTimeZoneProviders.Tzdb["US/Central"];

            var time = Instant.FromDateTimeUtc(DateTime.SpecifyKind(dateTime, DateTimeKind.Utc))

                          .InZone(timeZone)

                          .ToDateTimeUnspecified();

            return String.Format("{0:F}", time);

        }

}