Fix daylight savings code on Windows altogether

Reverted the previous change, the local timezone adjustment should not include
the daylight savings, because in a long running program that runs across the
DST boundary, the timezone doesn't change, but the DST adjustment does. That
is why LocalTZA is always used in conjunction with a call to DaylightSavingTA,
which unfortunately had a silly bug on Windows:

It was assumed that _localtime64_s returns zero on failure, similar to
localtime_r on Unix. However it is exactly the opposite, zero is returned
on success and an error code is returned on failure.

Change-Id: Ib324f09f290870630b66793882c5b121de445f05
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/src/qml/qml/v4/qv4dateobject.cpp b/src/qml/qml/v4/qv4dateobject.cpp
index b40820a7a0..3cf6cb1aeb 100644
--- a/src/qml/qml/v4/qv4dateobject.cpp
+++ b/src/qml/qml/v4/qv4dateobject.cpp
@@ -299,7 +299,8 @@ static inline double DaylightSavingTA(double t)
     struct tm tmtm;
 #if defined(_MSC_VER) && _MSC_VER >= 1400
     __time64_t  tt = (__time64_t)(t / msPerSecond);
-    if (!_localtime64_s(&tmtm, &tt))
+    // _localtime_64_s returns non-zero on failure
+    if (_localtime64_s(&tmtm, &tt) != 0)
 #else
     long int tt = (long int)(t / msPerSecond);
     if (!localtime_r((const time_t*) &tt, &tmtm))
@@ -634,10 +635,8 @@ static double getLocalTZA()
     return double(locl - globl) * 1000.0;
 #else
     TIME_ZONE_INFORMATION tzInfo;
-    LONG daylightBias = 0;
-    if (GetTimeZoneInformation(&tzInfo) == TIME_ZONE_ID_DAYLIGHT)
-        daylightBias = tzInfo.DaylightBias;
-    return -(tzInfo.Bias + daylightBias)* 60.0 * 1000.0;
+    GetTimeZoneInformation(&tzInfo);
+    return -tzInfo.Bias * 60.0 * 1000.0;
 #endif
 }