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Date: Tue, 23 Mar 1999 10:29:58 -0500
Message-Id: <199903231529.KAA15963@envy.delorie.com>
From: DJ Delorie <dj AT delorie DOT com>
To: Stefan DOT Weil AT de DOT heidelberg DOT com
CC: cygwin AT sourceware DOT cygnus DOT com
In-reply-to: 
	<7B9327EED0AAD211B0750090270F68EC2A16E9 AT hdhexmbx02 DOT ger02 DOT heidelberg DOT com>
	(Stefan DOT Weil AT de DOT heidelberg DOT com)
Subject: Re: Daylight saving bug in winsup/times.cc
References:  <7B9327EED0AAD211B0750090270F68EC2A16E9 AT hdhexmbx02 DOT ger02 DOT heidelberg DOT com>


> (gdb) p tz
> $9 = {Bias = -60, StandardName = {87, 101, 115, 116, 101, 117, 114, 111,
> 112,
>     228, 105, 115, 99, 104, 101, 32, 78, 111, 114, 109, 97, 108, 122, 101,
>     105, 116, 0, 0, 0, 0, 0, 0}, StandardDate = {wYear = 0, wMonth = 10,
>     wDayOfWeek = 0, wDay = 5, wHour = 3, wMinute = 0, wSecond = 0,
>     wMilliseconds = 0}, StandardBias = 0, DaylightName = {87, 101, 115, 116,
>     101, 117, 114, 111, 112, 228, 105, 115, 99, 104, 101, 32, 83, 111, 109,
>     109, 101, 114, 122, 101, 105, 116, 0, 0, 0, 0, 0, 0}, DaylightDate = {
>     wYear = 0, wMonth = 3, wDayOfWeek = 0, wDay = 5, wHour = 2, wMinute = 0,
>     wSecond = 0, wMilliseconds = 0}, DaylightBias = -60}
>
> According to the Microsoft documentation (see online help from Dev
> Studio), wYear == 0 needs a different algorithm. This algorithm is
> not implemented in function localtime, file winsup/times.cc, so
> localtime fails.
>
> Our registry entry simply says that daylight saving time starts at
> the last (wDay = 5) sunday (wDayOfWeek = 0) in march (wMonth = 3)
> every year (wYear = 0) at 2 AM (wHour = 2, wMinute = 0).  This is
> correct - it starts next sunday! CYGWIN thinks it already has
> started and incorrectly adds 60 minutes.

Cygwin uses the Bias field.  In your example, it's set to -60, which
means that daylight savings time has already started.  The MSDN docs
desribe this field as "Specifies the current bias, in minutes, for
local time translation on this computer."  So, the information in the
Bias field, for your computer, is currently wrong.

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