TimeZone em C#, uma forma simples de utilizar time zones em C#

TimeZone.cs

using System;

namespace TimeZone
{
    class Program
    {
        private static void Main(string[] args)
        {
            Console.WriteLine("Data/Hora atual         UTC : {0}", DateTime.UtcNow.ToString("dd/MM/yyyy HH:mm:ss"));
            Console.WriteLine("Data/Hora (UTC -4 Rondônia) : {0}", DateTime.UtcNow.AddHours(-4).ToString("dd/MM/yyyy HH:mm:ss"));
            Console.WriteLine("Data/Hora (UTC -3 Brasilia) : {0}", DateTime.UtcNow.AddHours(-3).ToString("dd/MM/yyyy HH:mm:ss"));
            Console.WriteLine("Data/Hora (UTC +8 Pequim  ) : {0}", DateTime.UtcNow.AddHours(+8).ToString("dd/MM/yyyy HH:mm:ss"));
        }
    }
}

Referencias:
http://msdn.microsoft.com/pt-br/library/system.datetime.utcnow.aspx
http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx