public static void Main()
DateTime utc = new DateTime(2021, 10, 23, 23, 0, 0, DateTimeKind.Utc);
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time");
DateTime initialTime = TimeZoneInfo.ConvertTimeFromUtc(utc, tzi);
Console.WriteLine("Supplied UTC time : " + utc.ToString("dd-MM-yyyy HH:mm"));
Console.WriteLine("Converted to GMT : " + initialTime.ToString("dd-MM-yyyy HH:mm"));
Console.WriteLine(string.Empty);
DateTime theirTime = utc.ToUniversalTime();
Console.WriteLine("Converted time : " + theirTime.ToString("dd-MM-yyyy HH:mm"));