Oh things are easy when you know how. I've been trying to do this for ages and then I got asked by Saad to help. Start by performing
IEnumerable<TimeZoneInfo> tzis = TimeZoneInfo.GetSystemInfos();
Then have a look to find the correct ID from the 87 items e.g. "Eastern Standard Time";
DateTime usTime = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow,
TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"));
Thanks Saad.