Implementation of zoneinfo (Olson, tz) database in .NET c-sharp csharp

[yoshito_umaoka at us.ibm.com]

Paul Eggert <eggert at CS.UCLA.EDU> wrote on 06/22/2007 10:55:28 AM:

> yoshito_umaoka at us.ibm.com writes:
> 
> > Windows used to support only a pair of DST start/end rules per zone,
> > but MS finlally implemented a framework for supporting historic
> > changes since Windows Vista.
> >
> > http://msdn2.microsoft.com/en-us/library/ms724253.aspx
> 
> That URL says that the framework isn't implemented yet.  The server
> side is scheduled to go out in Windows Server 2008 (aka "Longhorn").
> 

Right.  That's why I wrote - "since Windows Vista".

> Also, as far as I can tell, the client side supports only one rule
> change.  For example, in the US a single Vista setting might support
> both 1987-2006 and post-2006 time stamps, but it wouldn't also support
> pre-1987 time stamps.  At least, that is what I think
> <http://msdn2.microsoft.com/en-us/vstudio/bb264729.aspx> says (it's a
> bit hard to follow).  I don't use Vista so I can't easily verify this
> myself, but if this information is incorrect, please let us know, as
> the Wikipedia entry
> <http://en.wikipedia.org/wiki/Daylight_saving_time#Microsoft_Windows>
> should get corrected.

I think what you wrote is true at least for now.  I actually do not
have a copy of Windows Vista, but I once checked the keys on someone
else's system briefly.  What I found was, as you described, some
zones has one previous rule change.  But, regarding to the API and
KB docs, my understanding is that you can add historic/future rules
as many as you want and MS would do it for any future changes.  So
my point is - Windows Vista (and Longhorn) should be capable to
support proper time stamps before 1986, but the data is not provided
by MS at least for now.

Yoshito