#3509: fix dst and utcOffset handling for Dublin time zone

Foundation/include/Poco/Timezone.h

@@ -32,32 +32,44 @@ public:
 	static int utcOffset();
 		/// Returns the offset of local time to UTC, in seconds.
 		///     local time = UTC + utcOffset() + dst().
-		
+
 	static int dst();
 		/// Returns the daylight saving time offset in seconds if
 		/// daylight saving time is in use.
 		///     local time = UTC + utcOffset() + dst().
-	
+
 	static bool isDst(const Timestamp& timestamp);
 		/// Returns true if daylight saving time is in effect
 		/// for the given time. Depending on the operating system
 		/// platform this might only work reliably for certain
 		/// date ranges, as the C library's localtime() function
 		/// is used.
-		
+
 	static int tzd();
 		/// Returns the time zone differential for the current timezone.
 		/// The timezone differential is computed as utcOffset() + dst()
 		/// and is expressed in seconds.
-	
+
 	static std::string name();
 		/// Returns the timezone name currently in effect.
-		
+
 	static std::string standardName();
 		/// Returns the timezone name if not daylight saving time is in effect.
-		
+
 	static std::string dstName();
 		/// Returns the timezone name if daylight saving time is in effect.
+
+#if !defined(POCO_OS_FAMILY_WINDOWS)
+	static int utcOffset(const Poco::Timestamp& timestamp);
+		/// Returns the offset of local time to UTC
+		/// for the given time, in seconds.
+		///     local time = UTC + utcOffset() + dst().
+
+	static int dst(const Poco::Timestamp& timestamp);
+		/// Returns the daylight saving time offset in seconds if
+		/// daylight saving time is in use for the given time.
+		///     local time = UTC + utcOffset() + dst().
+#endif
 };
 
 

Foundation/src/LocalDateTime.cpp

@@ -277,7 +277,7 @@ void LocalDateTime::determineTzd(bool adjust)
  		if (err) broken = nullptr;
 #endif
 		if (!broken) throw Poco::SystemException("cannot get local time");
-		_tzd = (Timezone::utcOffset() + ((broken->tm_isdst == 1) ? 3600 : 0));
+		_tzd = (Timezone::utcOffset() + Timezone::dst(_dateTime.timestamp()));
 #else
 		std::tm broken;
 #if defined(POCO_VXWORKS) && (defined(_VXWORKS_COMPATIBILITY_MODE) || (defined(_WRS_VXWORKS_MAJOR) && ((_WRS_VXWORKS_MAJOR < 6) || ((_WRS_VXWORKS_MAJOR == 6)  && (_WRS_VXWORKS_MINOR < 9)))))
@@ -318,7 +318,7 @@ std::time_t LocalDateTime::dstOffset(int& dstOffset) const
 	local = std::mktime(&broken);
 #endif
 
-	dstOffset = (broken.tm_isdst == 1) ? 3600 : 0;
+	dstOffset = (broken.tm_isdst == 1) ? Timezone::dst(_dateTime.timestamp()) : 0;
 	return local;
 }
 

Foundation/src/Timezone_UNIX.cpp

@@ -28,34 +28,24 @@ public:
 	{
 		tzset();
 	}
-	
-	int timeZone()
-	{
-		Poco::FastMutex::ScopedLock lock(_mutex);
 
-	#if defined(__APPLE__)  || defined(__FreeBSD__) || defined (__OpenBSD__) || POCO_OS == POCO_OS_ANDROID // no timezone global var
+	static long gmtOffset(const struct std::tm& t)
-		std::time_t now = std::time(NULL);
+	{
-		struct std::tm t;
+	#if defined(__CYGWIN__)
-		gmtime_r(&now, &t);
+		return t.__TM_GMTOFF;
-		std::time_t utc = std::mktime(&t);
-		return now - utc;
-	#elif defined(__CYGWIN__)
-		tzset();
-		return -_timezone;
 	#else
-		tzset();
+		return t.tm_gmtoff;
-		return -timezone;
 	#endif
 	}
-	
+
 	const char* name(bool dst)
 	{
 		Poco::FastMutex::ScopedLock lock(_mutex);
 
-		tzset();		
+		tzset();
 		return tzname[dst ? 1 : 0];
 	}
-		
+
 private:
 	Poco::FastMutex _mutex;
 };
@@ -64,19 +54,39 @@ private:
 static TZInfo tzInfo;
 
 
-int Timezone::utcOffset()
+int Timezone::utcOffset(const Poco::Timestamp& timestamp)
 {
-	return tzInfo.timeZone();
+	std::time_t time = timestamp.epochTime();
+	struct std::tm local;
+	if (!localtime_r(&time, &local))
+		throw Poco::SystemException("cannot get UTC offset");
+	struct std::tm utc;
+	gmtime_r(&time, &utc);
+	std::time_t utctime = std::mktime(&utc);
+	return time - utctime;
 }
 
-	
+
+int Timezone::utcOffset()
+{
+	return utcOffset(Poco::Timestamp());
+}
+
+
 int Timezone::dst()
 {
-	std::time_t now = std::time(NULL);
+	return dst(Poco::Timestamp());
-	struct std::tm t;
+}
-	if (!localtime_r(&now, &t))
+
+
+int Timezone::dst(const Poco::Timestamp& timestamp)
+{
+	std::time_t time = timestamp.epochTime();
+	struct std::tm local;
+	if (!localtime_r(&time, &local))
 		throw Poco::SystemException("cannot get local time DST offset");
-	return t.tm_isdst == 1 ? 3600 : 0;
+	long dst = TZInfo::gmtOffset(local) - utcOffset(timestamp);
+	return local.tm_isdst == 1 ? dst : 0;
 }
 
 
@@ -88,19 +98,19 @@ bool Timezone::isDst(const Timestamp& timestamp)
 	return tms->tm_isdst > 0;
 }
 
-	
+
 std::string Timezone::name()
 {
 	return std::string(tzInfo.name(dst() != 0));
 }
 
-	
+
 std::string Timezone::standardName()
 {
 	return std::string(tzInfo.name(false));
 }
 
-	
+
 std::string Timezone::dstName()
 {
 	return std::string(tzInfo.name(true));

Foundation/testsuite/src/LocalDateTimeTest.cpp

@@ -65,7 +65,7 @@ void LocalDateTimeTest::testGregorian1()
 	//          the one on 1970-1-1
 	//assertTrue (dt.tzd() == Timezone::tzd());
 	assertTrue (dt.julianDay() == 2440587.5);
-	
+
 	dt.assign(2001, 9, 9, 1, 46, 40);
 	assertTrue (dt.year() == 2001);
 	assertTrue (dt.month() == 9);
@@ -92,7 +92,7 @@ void LocalDateTimeTest::testGregorian2()
 	assertTrue (dt.millisecond() == 0);
 	assertTrue (dt.dayOfWeek() == 4);
 	assertTrue (dt.tzd() == 2*3600);
-	
+
 	dt.assign(-7*3600, 2001, 9, 9, 1, 46, 40, 0, 0);
 	assertTrue (dt.year() == 2001);
 	assertTrue (dt.month() == 9);
@@ -134,12 +134,12 @@ void LocalDateTimeTest::testConversions()
 	assertTrue (dt5.millisecond() == 234);
 	assertTrue (dt5.dayOfWeek() == 5);
 	assertTrue (dt5.tzd() == -4*3600);
-	
+
 	DateTime dt6(2005, 1, 28, 14, 24, 44, 234, 0);
 	LocalDateTime dt7(3600, dt6);
 	LocalDateTime dt8(3600, dt6, false);
 	LocalDateTime dt9(3600, dt6, true);
-	
+
 	assertTrue (dt7.hour() == 15);
 	assertTrue (dt8.hour() == 14);
 	assertTrue (dt9.hour() == 15);
@@ -169,9 +169,9 @@ void LocalDateTimeTest::testCalcs()
 	assertTrue (dt1.week(DateTime::MONDAY) == 1);
 	dt1.assign(2007, 12, 31);
 	assertTrue (dt1.week(DateTime::MONDAY) == 53);
-	
+
 	// Jan 1 is Mon
-	dt1.assign(2001, 1, 1);  
+	dt1.assign(2001, 1, 1);
 	assertTrue (dt1.week() == 1);
 	dt1.assign(2001, 1, 7);
 	assertTrue (dt1.week() == 1);
@@ -205,7 +205,7 @@ void LocalDateTimeTest::testCalcs()
 	assertTrue (dt1.week() == 3);
 	dt1.assign(2003, 1, 20);
 	assertTrue (dt1.week() == 4);
-	
+
 	// Jan 1 is Thu
 	dt1.assign(2004, 1, 1);
 	assertTrue (dt1.week() == 1);
@@ -241,7 +241,7 @@ void LocalDateTimeTest::testCalcs()
 	assertTrue (dt1.week() == 2);
 	dt1.assign(2000, 1, 17);
 	assertTrue (dt1.week() == 3);
-	
+
 	// Jan 1 is Sun
 	dt1.assign(1995, 1, 1);
 	assertTrue (dt1.week() == 0);
@@ -262,7 +262,7 @@ void LocalDateTimeTest::testAMPM()
 	assertTrue (dt1.isAM());
 	assertTrue (!dt1.isPM());
 	assertTrue (dt1.hourAMPM() == 12);
-	
+
 	dt1.assign(2005, 1, 1, 12, 15, 30);
 	assertTrue (!dt1.isAM());
 	assertTrue (dt1.isPM());
@@ -280,14 +280,14 @@ void LocalDateTimeTest::testRelational1()
 	LocalDateTime dt1(2005, 1, 1, 0, 15, 30);
 	LocalDateTime dt2(2005, 1, 2, 0, 15, 30);
 	LocalDateTime dt3(dt1);
-	
+
 	assertTrue (dt1 < dt2);
 	assertTrue (dt1 <= dt2);
 	assertTrue (dt2 > dt1);
 	assertTrue (dt2 >= dt1);
 	assertTrue (dt1 != dt2);
 	assertTrue (!(dt1 == dt2));
-	
+
 	assertTrue (dt1 == dt3);
 	assertTrue (!(dt1 != dt3));
 	assertTrue (dt1 >= dt3);
@@ -309,7 +309,7 @@ void LocalDateTimeTest::testRelational2()
 	assertTrue (dt2 >= dt1);
 	assertTrue (dt1 != dt2);
 	assertTrue (!(dt1 == dt2));
-	
+
 	assertTrue (dt1 == dt3);
 	assertTrue (!(dt1 != dt3));
 	assertTrue (dt1 >= dt3);
@@ -323,13 +323,13 @@ void LocalDateTimeTest::testArithmetics1()
 {
 	LocalDateTime dt1(2005, 1, 1, 0, 15, 30);
 	LocalDateTime dt2(2005, 1, 2, 0, 15, 30);
-	
+
 	Timespan s = dt2 - dt1;
 	assertTrue (s.days() == 1);
-	
+
 	LocalDateTime dt3 = dt1 + s;
 	assertTrue (dt3 == dt2);
-	
+
 	dt3 -= s;
 	assertTrue (dt3 == dt1);
 	dt1 += s;
@@ -341,13 +341,13 @@ void LocalDateTimeTest::testArithmetics2()
 {
 	LocalDateTime dt1(2*3600, 2005, 1, 1, 15, 30, 0, 0, 0);
 	LocalDateTime dt2(5*3600, 2005, 1, 2, 18, 30, 0, 0, 0);
-	
+
 	Timespan s = dt2 - dt1;
 	assertTrue (s.days() == 1);
-	
+
 	LocalDateTime dt3 = dt1 + s;
 	assertTrue (dt3 == dt2);
-	
+
 	dt3 -= s;
 	assertTrue (dt3 == dt1);
 	dt1 += s;
@@ -359,7 +359,7 @@ void LocalDateTimeTest::testSwap()
 {
 	LocalDateTime dt1(2005, 1, 1, 0, 15, 30);
 	LocalDateTime dt2(2005, 1, 2, 0, 15, 30);
-	
+
 	assertTrue (dt1 < dt2);
 	dt1.swap(dt2);
 	assertTrue (dt2 < dt1);
@@ -454,6 +454,37 @@ void LocalDateTimeTest::testTimezone()
 }
 
 
+void LocalDateTimeTest::testTimezone2()
+{
+#if defined(POCO_OS_FAMILY_UNIX)
+	std::vector<std::string> timezones = {
+		"/usr/share/zoneinfo/America/Los_Angeles",
+		"/usr/share/zoneinfo/Europe/London",
+		"/usr/share/zoneinfo/Europe/Dublin", // special winter time of Ireland
+		"/usr/share/zoneinfo/Europe/Prague",
+	};
+
+	std::cout << "\n";
+
+	for (const std::string& tz : timezones)
+	{
+		setenv("TZ", tz.c_str(), 1); // POSIX-specific
+		std::vector<LocalDateTime> times = {
+			LocalDateTime(2022, 06, 29), // summer period
+			LocalDateTime(2022, 01, 29), // winter period
+		};
+		for (const LocalDateTime& ldt : times) {
+			std::time_t t = ldt.timestamp().epochTime();
+			std::tm then;
+			then = *std::localtime(&t);
+			assertTrue (then.tm_gmtoff == ldt.tzd());
+		}
+		unsetenv("TZ");
+	}
+#endif
+}
+
+
 void LocalDateTimeTest::setUp()
 {
 }
@@ -479,6 +510,7 @@ CppUnit::Test* LocalDateTimeTest::suite()
 	CppUnit_addTest(pSuite, LocalDateTimeTest, testArithmetics2);
 	CppUnit_addTest(pSuite, LocalDateTimeTest, testSwap);
 	CppUnit_addTest(pSuite, LocalDateTimeTest, testTimezone);
+	CppUnit_addTest(pSuite, LocalDateTimeTest, testTimezone2);
 
 	return pSuite;
 }

Foundation/testsuite/src/LocalDateTimeTest.h

@@ -35,6 +35,7 @@ public:
 	void testArithmetics2();
 	void testSwap();
 	void testTimezone();
+	void testTimezone2();
 
 	void setUp();
 	void tearDown();