Get timezone from DateTime

No.

A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism.

A quote from an excellent article here. A must read for every .Net developer.

So my advice is to write a little wrapper class that suits your needs.

DateTime itself contains no real timezone information. It may know if it's UTC or local, but not what local really means.

DateTimeOffset is somewhat better - that's basically a UTC time and an offset. However, that's still not really enough to determine the timezone, as many different timezones can have the same offset at any one point in time. This sounds like it may be good enough for you though, as all you've got to work with when parsing the date/time is the offset.

The support for time zones as of .NET 3.5 is a lot better than it was, but I'd really like to see a standard "ZonedDateTime" or something like that - a UTC time and an actual time zone. It's easy to build your own, but it would be nice to see it in the standard libraries.

EDIT: Nearly four years later, I'd now suggest using Noda Time which has a rather richer set of date/time types. I'm biased though, as the main author of Noda Time :)

There is a public domain TimeZone library for .NET. Really useful. It will answer your needs.

Solving the general-case timezone problem is harder than you think.