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Is there a generic TimeZoneInfo for Central Europe that takes into consideration both CET and CEST into one?

I have an app that is doing the following:

TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Central European Standard Time"); 
DateTimeOffset dto = new DateTimeOffset(someDate, tzi.BaseUtcOffset);
var utcDate = dto.ToUniversalTime().DateTime;

The problem is that this is returning the wrong utcDate because the BaseUtcOffset is +1 instead of +2. It appears that CET has DST as well and depending on the time of the year it is +1 or +2.

Jonas Stawski
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2 Answers2

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Firstly, I'd like to applaud mgnoonan's answer of using Noda Time :) But if you're feeling less adventurous...

You're already using the right time zone - but you shouldn't be using BaseUtcOffset which is documented not to be about DST:

Gets the time difference between the current time zone's standard time and Coordinated Universal Time (UTC).

It can't possibly take DST into consideration when you're not providing it a DateTime to fetch the offset for :)

Assuming someDate is a DateTime, you could use:

DateTimeOffset dto = new DateTimeOffset(someDate, tzi.GetUtcOffset(someDate));

Or just ConvertTimeToUtc:

var utcDate = TimeZoneInfo.ConvertTimeToUtc(someDate, tzi);

Note that you should work out what you want to do if your local time occurs twice due to a DST transition, or doesn't occur at all.

Jon Skeet
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  • I knew I should have just waited for you to answer. ;) – mgnoonan Apr 05 '12 at 10:56
  • Great explanation. Although Noda Time might be the right tool, this worked and is the best solution for the current project. – Jonas Stawski Apr 06 '12 at 14:20
  • Just a minor comment: ConvertTimeToUtc is now a static method so you need to call var utcDate = TimeZoneInfo.ConvertTimeToUtc(someDate, tzi) – Eoin Jan 18 '16 at 19:27
  • @Eoin: How odd - I wonder how I got that wrong. Will fix. (There are a bunch of static methods in `TimeZoneInfo` taking a `TimeZoneInfo` as a parameter. I've never understood why...) – Jon Skeet Jan 18 '16 at 19:36
4

Maybe Noda Time can help you out?

mgnoonan
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