TimeZone::ToUniversalTime Method
Returns the Coordinated Universal Time (UTC) that corresponds to a specified time.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- time
- Type: System::DateTime
A date and time.
Return Value
Type: System::DateTimeA DateTime object whose value is the Coordinated Universal Time (UTC) that corresponds to time.
If the local time zone observes daylight saving time, ToUniversalTime applies the current adjustment rule to the time parameter when performing the conversion.
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The ToUniversalTime method recognizes only the current daylight saving time adjustment rule for the local time zone. As a result, it is guaranteed to accurately return the Coordinated Universal Time (UTC) corresponding to a particular local time only during the period in which the latest adjustment rule is in effect. It may return inaccurate results if time is a historic date and time value that was subject to a previous adjustment rule. |
If the time parameter is an ambiguous time, the method assumes that it is a standard time. (An ambiguous time is one that can map either to a standard time or to a daylight saving time in the local time zone.) If time is an invalid time, the method simply subtracts the local time from the local time zone's UTC offset to return UTC. (An invalid time is one that does not exist because of the application of daylight saving time adjustment rules.)
Because time is interpreted in relation to the current time zone on the current system, the date and time returned by this method can differ if an application is run on different computers or on the same computer with different time zones. For cases in which a date and time value must represent a single, unambiguous point in time, use a DateTimeOffset value to represent the local time.
The ToUniversalTime method corresponds to the TimeZoneInfo::ConvertTimeToUtc(DateTime) method overload with a DateTime parameter whose Kind property does not equal DateTimeKind::Utc. Whenever possible, use the TimeZoneInfo::ConvertTimeToUtc(DateTime) method overload.
The following example uses the ToUniversalTime method to return the Coordinated Universal Time (UTC) times that correspond to selected local times.
// 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.
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