DateTime does not know its timezone offset. There is no built-in method to return the offset or the timezone name (e.g. EAT, CEST, EST etc).
Like suggested by others, you can convert your date to UTC:
DateTime localtime = new DateTime.Now;
var utctime = localtime.ToUniversalTime();
and then only calculate the difference:
TimeSpan difference = localtime - utctime;
Also you may convert one time to another by using the DateTimeOffset:
DateTimeOffset targetTime = DateTimeOffset.Now.ToOffset(new TimeSpan(5, 30, 0));
But this is sort of lossy compression - the offset alone cannot tell you which time zone it is as two different countries may be in different time zones and have the same time only for part of the year (eg. South Africa and Europe). Also, be aware that summer daylight saving time may be introduced at different dates (EST vs CET - a 3-week difference).
You can get the name of your local system time zone using TimeZoneInfo class:
TimeZoneInfo localZone = TimeZoneInfo.Local;
localZone.IsDaylightSavingTime(localtime) ? localZone.DaylightName : localZone.StandardName
I agree with Gerrie Schenck, please read the article he suggested.