TimeZone::IsDaylightSavingTime Method (DateTime)
Returns a value indicating whether the specified date and time is within a daylight saving time period.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- time
- Type: System::DateTime
A date and time.
Return Value
Type: System::Booleantrue if time is in a daylight saving time period; otherwise, false.
The year to which the daylight saving time period applies is derived from the time parameter.
Because the TimeZone class supports a single daylight saving time adjustment rule, the IsDaylightSavingTime(DateTime) method applies the current adjustment rule to any date, regardless of whether the adjustment rule was in effect on that date. Assuming that the operating system itself has accurate historic daylight saving time data, a more accurate result is available by using the TimeZoneInfo::IsDaylightSavingTime method. Whenever possible, use the TimeZoneInfo::IsDaylightSavingTime method.
The following example uses the IsDaylightSavingTime method to determine whether selected dates are within daylight saving time for any year.
// Example of the TimeZone::IsDaylightSavingTime( DateTime ), // TimeZone::IsDaylightSavingTime( DateTime, DaylightTime ), and // TimeZone::ToUniversalTime( DateTime ) methods. using namespace System; using namespace System::Globalization; int main() { String^ headFmt = "{0,-22}{1,-10}{2,-10}{3,-10}{4}"; // Get the local time zone and a base local time. TimeZone^ localZone = TimeZone::CurrentTimeZone; DateTime localTime = DateTime(2001,1,1); Console::WriteLine( "This example of \n" " TimeZone::IsDaylightSavingTime( DateTime ), \n" " TimeZone::IsDaylightSavingTime( " "DateTime, DaylightTime* ), and \n" " TimeZone::ToUniversalTime( DateTime )\n" "generates the following output, which varies " "depending on the \ntime zone in which it is run.\n" ); Console::WriteLine( "The example creates several local " "times and the corresponding \nCoordinated Universal " "Times (UTC) and shows if they occur in \ndaylight " "saving time (DST), both for specified years " "and for \nany year.\n" ); Console::WriteLine( "Local time: {0}\n", localZone->StandardName ); Console::WriteLine( headFmt, "Local Date and Time", "2001 DST?", "2002 DST?", "Any DST?", "Corresponding UTC" ); Console::WriteLine( headFmt, "-------------------", "---------", "---------", "--------", "-----------------" ); // Create DaylightTime objects for specific years. DaylightTime^ daylight2001 = localZone->GetDaylightChanges( 2001 ); DaylightTime^ daylight2002 = localZone->GetDaylightChanges( 2002 ); // Generate several local times. for ( int loopX = 0; loopX <= 10; loopX++ ) { // Calculate the corresponding UTC. DateTime utcTime = localZone->ToUniversalTime( localTime ); // Show if dates and times occur in daylight saving // time, for specified years and for any year. Console::WriteLine( "{0,-22:yyyy-MM-dd HH:mm}" "{1,-10}{2,-10}{3,-10}{4:yyyy-MM-dd HH:mm}", localTime, TimeZone::IsDaylightSavingTime( localTime, daylight2001 ), TimeZone::IsDaylightSavingTime( localTime, daylight2002 ), localZone->IsDaylightSavingTime( localTime ), utcTime ); // Advance to another local time. localTime = localTime.AddDays( 109.1 ); } } /* This example of TimeZone::IsDaylightSavingTime( DateTime ), TimeZone::IsDaylightSavingTime( DateTime, DaylightTime* ), and TimeZone::ToUniversalTime( DateTime ) generates the following output, which varies depending on the time zone in which it is run. The example creates several local times and the corresponding Coordinated Universal Times (UTC) and shows if they occur in daylight saving time (DST), both for specified years and for any year. Local time: Pacific Standard Time Local Date and Time 2001 DST? 2002 DST? Any DST? Corresponding UTC ------------------- --------- --------- -------- ----------------- 2001-01-01 00:00 False False False 2001-01-01 08:00 2001-04-20 02:24 True False True 2001-04-20 09:24 2001-08-07 04:48 True False True 2001-08-07 11:48 2001-11-24 07:12 False False False 2001-11-24 15:12 2002-03-13 09:36 False False False 2002-03-13 17:36 2002-06-30 12:00 False True True 2002-06-30 19:00 2002-10-17 14:24 False True True 2002-10-17 21:24 2003-02-03 16:48 False False False 2003-02-04 00:48 2003-05-23 19:12 False False True 2003-05-24 02:12 2003-09-09 21:36 False False True 2003-09-10 04:36 2003-12-28 00:00 False False False 2003-12-28 08:00 */
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.