GMT time matching in c# mvc not working

Question

GMT time matching in c# mvc not working.

Problems having fetch of time difference is not correct.

Here is the code i am tred but not working:

DateTime newDateTime = Convert.ToDateTime(DateNw).Add(TimeSpan.Parse(Time));
                ////New Zealand
                string nzTimeZoneKey = Country + " Standard Time";
                string date = newDateTime.ToUniversalTime().ToString("u");
                DateTime localDateTime = DateTime.Parse(date);
                DateTime utcDateTime = localDateTime.ToUniversalTime();
                TimeZoneInfo nzTimeZone = TimeZoneInfo.FindSystemTimeZoneById(nzTimeZoneKey);
                DateTime nzDateTime = TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, nzTimeZone);
                //return nzDateTime;

The above code working for India and afganistan working very well but if i change the country between india and fiji it is not working.

I want GMT time matching for all the country where i can differnciate two country time. Any suggestion???