Display UTC Datetime to user defined timezone - asp.net-mvc-4

Question

I have dates in UTC in database, and I have the user timezone in their preferences table.
I have an extension method to convert from UTC to user time:
public static DateTime ToClientTime(this DateTime dt)
{
TimeZoneInfo cstZone = TimeZoneInfo.FindSystemTimeZoneById("SA Pacific Standard Time"); //Hardcoded timezone
return TimeZoneInfo.ConvertTimeFromUtc(dt, cstZone);
}
As you can see in the code below, for now it has a hardcoded time zone name, and I should pass by parameter that value (passing the user timezone).
In CurrentThread I set the user culture, so all code in this request behaves in that culture (date formats, resources, number formats). There is a way to store the user's timezone in a global object like CurrentThread or something like that?
What I'm trying to accomplish is avoid passing the time zone to the above extension method, and instead get the timezone from a global object like CurrentThread. The extension method will be called from Controller code and also from Views.

Answer 1

You have a base time like UTC, right? Not you have a user specified time zone in data base. So now you can either add or subtract from the UTC time zone depending on the need.
Probably addition can provide a simple solution.
Example:
Name ----------TimeZone
------------------------
Nick ------- UTC - 6
Hary ------- UTC + 1
So, if the current UTC time is 7 PM or 18:00 then
Nick = 18-6 = 12 / 12 PM
Harry = 18+1 = 19 / 8PM