TimeZoneInfo.Local vs TimeZoneInfo.FindSystemTimeZoneById

Question

I\'ve been working with the DateTime and TimeZoneInfo classes and I ran into an interesting result with the following code:

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Answer 1

I did a little bit of reflecting and I believe the inconsistency stems from how System.TimeZoneInfo+CachedData.GetCorrespondingKind(TimeZoneInfo timeZone) returns DateTimeKind.Local only in the case where timeZone == this.m_localTimeZone (ie, when the argument was the same instance as the TimeZoneInfo.Local property is based on).

In the case where you pass this other TimeZoneInfo instance you got from TimeZoneInfo.FindSystemTimeZoneById I expect that it returns DateTimeKind.Unspecified.

This will (probably among other things) affect System.TimeZoneInfo.IsDaylightSavingTime(DateTime dateTime) where, in the case where dateTime.Kind is local, it does a conversion between essentially TimeZoneInfo.Local and your TimeZoneInfo instance and bases the conversion on what GetCorrespondingKind says for the source and target timezones (the conversion returns the original datetime in the case where source and target are both local).