1 files changed, 57 insertions, 23 deletions

diff --git a/Source/WTF/wtf/DateMath.cpp b/Source/WTF/wtf/DateMath.cpp
index 654bd8d2d..1350e3040 100644
--- a/Source/WTF/wtf/DateMath.cpp
+++ b/Source/WTF/wtf/DateMath.cpp
@@ -121,18 +121,16 @@ static const int firstDayOfMonth[2][12] = {
     {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335}
 };
 
-#if !OS(WINCE)
 static inline void getLocalTime(const time_t* localTime, struct tm* localTM)
 {
-#if COMPILER(MINGW)
-    *localTM = *localtime(localTime);
-#elif COMPILER(MSVC)
+#if COMPILER(MSVC)
     localtime_s(localTM, localTime);
-#else
+#elif HAVE(LOCALTIME_R)
     localtime_r(localTime, localTM);
+#else
+    localtime_s(localTime, localTM);
 #endif
 }
-#endif
 
 bool isLeapYear(int year)
 {
@@ -166,7 +164,7 @@ static inline double daysFrom1970ToYear(int year)
     const double yearsToExcludeBy100Rule = floor(yearMinusOne / 100.0) - excludedLeapDaysBefore1971By100Rule;
     const double yearsToAddBy400Rule = floor(yearMinusOne / 400.0) - leapDaysBefore1971By400Rule;
 
-    return 365.0 * (year - 1970) + yearsToAddBy4Rule - yearsToExcludeBy100Rule + yearsToAddBy400Rule;
+    return 365.0 * (year - 1970.0) + yearsToAddBy4Rule - yearsToExcludeBy100Rule + yearsToAddBy400Rule;
 }
 
 double msToDays(double ms)
@@ -359,16 +357,56 @@ int equivalentYearForDST(int year)
     int product = (quotient) * 28;
 
     year += product;
-    ASSERT((year >= minYear && year <= maxYear) || (product - year == static_cast<int>(std::numeric_limits<double>::quiet_NaN())));
     return year;
 }
 
+#if OS(WINDOWS)
+typedef BOOL(WINAPI* callGetTimeZoneInformationForYear_t)(USHORT, PDYNAMIC_TIME_ZONE_INFORMATION, LPTIME_ZONE_INFORMATION);
+
+static callGetTimeZoneInformationForYear_t timeZoneInformationForYearFunction()
+{
+    static callGetTimeZoneInformationForYear_t getTimeZoneInformationForYear = nullptr;
+
+    if (getTimeZoneInformationForYear)
+        return getTimeZoneInformationForYear;
+
+    HMODULE module = ::GetModuleHandleW(L"kernel32.dll");
+    if (!module)
+        return nullptr;
+
+    getTimeZoneInformationForYear = reinterpret_cast<callGetTimeZoneInformationForYear_t>(::GetProcAddress(module, "GetTimeZoneInformationForYear"));
+
+    return getTimeZoneInformationForYear;
+}
+#endif
+
 static int32_t calculateUTCOffset()
 {
 #if OS(WINDOWS)
     TIME_ZONE_INFORMATION timeZoneInformation;
-    GetTimeZoneInformation(&timeZoneInformation);
-    int32_t bias = timeZoneInformation.Bias + timeZoneInformation.StandardBias;
+    DWORD rc = 0;
+
+    if (callGetTimeZoneInformationForYear_t timeZoneFunction = timeZoneInformationForYearFunction()) {
+        // If available, use the Windows API call that takes into account the varying DST from
+        // year to year.
+        SYSTEMTIME systemTime;
+        ::GetSystemTime(&systemTime);
+        rc = timeZoneFunction(systemTime.wYear, nullptr, &timeZoneInformation);
+        if (rc == TIME_ZONE_ID_INVALID)
+            return 0;
+    } else {
+        rc = ::GetTimeZoneInformation(&timeZoneInformation);
+        if (rc == TIME_ZONE_ID_INVALID)
+            return 0;
+    }
+
+    int32_t bias = timeZoneInformation.Bias;
+
+    if (rc == TIME_ZONE_ID_DAYLIGHT)
+        bias += timeZoneInformation.DaylightBias;
+    else if (rc == TIME_ZONE_ID_STANDARD || rc == TIME_ZONE_ID_UNKNOWN)
+        bias += timeZoneInformation.StandardBias;
+
     return -bias * 60 * 1000;
 #else
     time_t localTime = time(0);
@@ -424,16 +462,14 @@ static void UnixTimeToFileTime(time_t t, LPFILETIME pft)
  */
 static double calculateDSTOffset(time_t localTime, double utcOffset)
 {
-#if OS(WINCE)
-    UNUSED_PARAM(localTime);
-    UNUSED_PARAM(utcOffset);
-    return 0;
-#elif OS(WINDOWS)
+#if OS(WINDOWS)
     FILETIME utcFileTime;
     UnixTimeToFileTime(localTime, &utcFileTime);
     SYSTEMTIME utcSystemTime, localSystemTime;
-    FileTimeToSystemTime(&utcFileTime, &utcSystemTime);
-    SystemTimeToTzSpecificLocalTime(0, &utcSystemTime, &localSystemTime);
+    if (!::FileTimeToSystemTime(&utcFileTime, &utcSystemTime))
+        return 0;
+    if (!::SystemTimeToTzSpecificLocalTime(nullptr, &utcSystemTime, &localSystemTime))
+        return 0;
 
     double offsetTime = (localTime * msPerSecond) + utcOffset;
 
@@ -524,12 +560,10 @@ void initializeDates()
 
 static inline double ymdhmsToSeconds(int year, long mon, long day, long hour, long minute, double second)
 {
-    double days = (day - 32075)
-        + floor(1461 * (year + 4800.0 + (mon - 14) / 12) / 4)
-        + 367 * (mon - 2 - (mon - 14) / 12 * 12) / 12
-        - floor(3 * ((year + 4900.0 + (mon - 14) / 12) / 100) / 4)
-        - 2440588;
-    return ((days * hoursPerDay + hour) * minutesPerHour + minute) * secondsPerMinute + second;
+    int mday = firstDayOfMonth[isLeapYear(year)][mon - 1];
+    double ydays = daysFrom1970ToYear(year);
+
+    return (second + minute * secondsPerMinute + hour * secondsPerHour + (mday + day - 1 + ydays) * secondsPerDay);
 }
 
 // We follow the recommendation of RFC 2822 to consider all