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