This documentation is archived and is not being maintained.

TimeZone.GetDaylightChanges Method

Returns the daylight saving time period for a particular year.

[Visual Basic]
Public MustOverride Function GetDaylightChanges( _
   ByVal year As Integer _
) As DaylightTime
[C#]
public abstract DaylightTime GetDaylightChanges(
 int year
);
[C++]
public: virtual DaylightTime* GetDaylightChanges(
 int year
) = 0;
[JScript]
public abstract function GetDaylightChanges(
   year : int
) : DaylightTime;

Parameters

year
The year to which the daylight saving time period applies.

Return Value

A System.Globalization.DaylightTime instance containing the start and end date for daylight saving time in year.

Exceptions

Exception Type Condition
ArgumentOutOfRangeException year is less than 1 or greater than 9999.

Remarks

Only one daylight saving time period per year is supported.

If daylight saving time is not used in the current time zone, the return value is a DaylightTime, where the value of Start and End is DateTime.MinValue, and the value of DaylightTime.Delta is a TimeSpan initialized to 0 ticks.

Example

[Visual Basic, C#, C++] The following code example uses the GetDaylightChanges method to return the daylight saving time period and offset for selected years.

[Visual Basic] 
' Example of the TimeZone.GetDaylightChanges( Integer ) method.
Imports System
Imports System.Globalization
Imports Microsoft.VisualBasic

Module DaylightChangesDemo

    ' Get the local time zone and a base local time.
    Dim localZone As TimeZone = TimeZone.CurrentTimeZone

    Sub CreateDaylightTime( year As Integer )

        ' Create a DaylightTime object for the specified year.
        Dim daylight As DaylightTime = _
            localZone.GetDaylightChanges( year )

        ' Display the start and end dates and the time change.
        Console.WriteLine( "{0,-7}{1,-20:yyyy-MM-dd HH:mm}" & _
            "{2,-20:yyyy-MM-dd HH:mm}{3}", _
            year, daylight.Start, daylight.End, daylight.Delta )
    End Sub 

    Sub Main( )

        Const headFmt As String = "{0,-7}{1,-20}{2,-20}{3}"

        Console.WriteLine( _
            "This example of TimeZone.GetDaylightChanges( " & _
            "Integer ) generates the " & vbCrLf & "following " & _
            "output, which varies depending on the time zone " & _
            "in which " & vbCrLf & "it is run. The example " & _
            "creates DaylightTime objects for specified " & _
            vbCrLf & "years and displays the start and end dates " & _
            "and time change for " & vbCrLf &  "daylight " & _
            "saving time." & vbCrLf )

        ' Write a message explaining that start dates prior to 1986 
        ' in the en-US culture may not be correct.
        If CultureInfo.CurrentCulture.Name = "en-US" Then

            Console.WriteLine( _
                "Note: In the [en-US] culture, all start dates " & _
                "are calculated from " & vbCrLf & "the first " & _
                "Sunday in April, based on a standard set in " & _
                "1986. For " & vbCrLf & "dates prior to 1986, " & _
                "the calculated start date may not be accurate." )
        End If

        Console.WriteLine( vbCrLf & "Local time: {0}" & vbCrLf, _
            localZone.StandardName )

        Console.WriteLine( headFmt, "Year", "Start", "End", "Change" )
        Console.WriteLine( headFmt, "----", "-----", "---", "------" )

        CreateDaylightTime( 1960 )
        CreateDaylightTime( 1970 )
        CreateDaylightTime( 1980 )
        CreateDaylightTime( 1990 )
        CreateDaylightTime( 2000 )
        CreateDaylightTime( 2001 )
        CreateDaylightTime( 2002 )
        CreateDaylightTime( 2003 )
        CreateDaylightTime( 2004 )
        CreateDaylightTime( 2005 )
        CreateDaylightTime( 2020 )
        CreateDaylightTime( 2040 )
    End Sub 
End Module 

' This example of TimeZone.GetDaylightChanges( Integer ) generates the
' following output, which varies depending on the time zone in which
' it is run. The example creates DaylightTime objects for specified
' years and displays the start and end dates and time change for
' daylight saving time.
' 
' Note: In the [en-US] culture, all start dates are calculated from
' the first Sunday in April, based on a standard set in 1986. For
' dates prior to 1986, the calculated start date may not be accurate.
' 
' Local time: Pacific Standard Time
' 
' Year   Start               End                 Change
' ----   -----               ---                 ------
' 1960   1960-04-03 02:00    1960-10-30 02:00    01:00:00
' 1970   1970-04-05 02:00    1970-10-25 02:00    01:00:00
' 1980   1980-04-06 02:00    1980-10-26 02:00    01:00:00
' 1990   1990-04-01 02:00    1990-10-28 02:00    01:00:00
' 2000   2000-04-02 02:00    2000-10-29 02:00    01:00:00
' 2001   2001-04-01 02:00    2001-10-28 02:00    01:00:00
' 2002   2002-04-07 02:00    2002-10-27 02:00    01:00:00
' 2003   2003-04-06 02:00    2003-10-26 02:00    01:00:00
' 2004   2004-04-04 02:00    2004-10-31 02:00    01:00:00
' 2005   2005-04-03 02:00    2005-10-30 02:00    01:00:00
' 2020   2020-04-05 02:00    2020-10-25 02:00    01:00:00
' 2040   2040-04-01 02:00    2040-10-28 02:00    01:00:00

[C#] 
// Example of the TimeZone.GetDaylightChanges( int ) method.
using System;
using System.Globalization;

class DaylightChangesDemo
{
    // Get the local time zone and a base local time.
    static TimeZone localZone = TimeZone.CurrentTimeZone;

    static void CreateDaylightTime( int year )
    {
        // Create a DaylightTime object for the specified year.
        DaylightTime daylight = 
            localZone.GetDaylightChanges( year );

        // Display the start and end dates and the time change.
        Console.WriteLine( "{0,-7}{1,-20:yyyy-MM-dd HH:mm}" +
            "{2,-20:yyyy-MM-dd HH:mm}{3}", 
            year, daylight.Start, daylight.End, daylight.Delta );
    } 

    static void Main( )
    {
        const string headFmt = "{0,-7}{1,-20}{2,-20}{3}";

        Console.WriteLine(
            "This example of TimeZone.GetDaylightChanges( int ) " +
            "generates the \nfollowing output, which varies " +
            "depending on the time zone in which \nit is run. The " +
            "example creates DaylightTime objects for specified \n" +
            "years and displays the start and end dates and time " +
            "change for \ndaylight saving time.\n" );

        // Write a message explaining that start dates prior to 1986 
        // in the en-US culture may not be correct.
        if( CultureInfo.CurrentCulture.Name == "en-US" )
        {
            Console.WriteLine(
                "Note: In the [en-US] culture, all start dates are " +
                "calculated from \nthe first Sunday in April, " +
                "based on a standard set in 1986. For \ndates " +
                "prior to 1986, the calculated start date may not " +
                "be accurate." );
        }

        Console.WriteLine( "\nLocal time: {0}\n", 
            localZone.StandardName );

        Console.WriteLine( headFmt, "Year", "Start", "End", "Change" );
        Console.WriteLine( headFmt, "----", "-----", "---", "------" );

        CreateDaylightTime( 1960 );
        CreateDaylightTime( 1970 );
        CreateDaylightTime( 1980 );
        CreateDaylightTime( 1990 );
        CreateDaylightTime( 2000 );
        CreateDaylightTime( 2001 );
        CreateDaylightTime( 2002 );
        CreateDaylightTime( 2003 );
        CreateDaylightTime( 2004 );
        CreateDaylightTime( 2005 );
        CreateDaylightTime( 2020 );
        CreateDaylightTime( 2040 );
    } 
} 

/*
This example of TimeZone.GetDaylightChanges( int ) generates the
following output, which varies depending on the time zone in which
it is run. The example creates DaylightTime objects for specified
years and displays the start and end dates and time change for
daylight saving time.

Note: In the [en-US] culture, all start dates are calculated from
the first Sunday in April, based on a standard set in 1986. For
dates prior to 1986, the calculated start date may not be accurate.

Local time: Pacific Standard Time

Year   Start               End                 Change
----   -----               ---                 ------
1960   1960-04-03 02:00    1960-10-30 02:00    01:00:00
1970   1970-04-05 02:00    1970-10-25 02:00    01:00:00
1980   1980-04-06 02:00    1980-10-26 02:00    01:00:00
1990   1990-04-01 02:00    1990-10-28 02:00    01:00:00
2000   2000-04-02 02:00    2000-10-29 02:00    01:00:00
2001   2001-04-01 02:00    2001-10-28 02:00    01:00:00
2002   2002-04-07 02:00    2002-10-27 02:00    01:00:00
2003   2003-04-06 02:00    2003-10-26 02:00    01:00:00
2004   2004-04-04 02:00    2004-10-31 02:00    01:00:00
2005   2005-04-03 02:00    2005-10-30 02:00    01:00:00
2020   2020-04-05 02:00    2020-10-25 02:00    01:00:00
2040   2040-04-01 02:00    2040-10-28 02:00    01:00:00
*/ 

[C++] 
// Example of the TimeZone::GetDaylightChanges( int ) method.
#using <mscorlib.dll>
using namespace System;
using namespace System::Globalization;

void CreateDaylightTime( int year, TimeZone* localZone )
{
    // Create a DaylightTime object for the specified year.
    DaylightTime* daylight = 
        localZone->GetDaylightChanges( year );

    // Display the start and end dates and the time change.
    Console::WriteLine( S"{0,-7}{1,-20:yyyy-MM-dd HH:mm}" 
        S"{2,-20:yyyy-MM-dd HH:mm}{3}", 
        __box( year ), __box( daylight->Start ), 
        __box( daylight->End ), __box( daylight->Delta ) );
} 

void main( )
{
    String* headFmt = S"{0,-7}{1,-20}{2,-20}{3}";

    // Get the local time zone.
    TimeZone* localZone = TimeZone::CurrentTimeZone;

    Console::WriteLine(
        S"This example of TimeZone::GetDaylightChanges( int ) " 
        S"generates the \nfollowing output, which varies " 
        S"depending on the time zone in which \nit is run. The " 
        S"example creates DaylightTime objects for specified \n" 
        S"years and displays the start and end dates and time " 
        S"change for \ndaylight saving time.\n" );

    // Write a message explaining that start dates prior to 1986 
    // in the en-US culture may not be correct.
    // ( CultureInfo::CurrentCulture->Name == S"en-US" ) returns False.
    if( CultureInfo::CurrentCulture->Name->CompareTo( S"en-US" ) == 0 )
    {
        Console::WriteLine(
            S"Note: In the [en-US] culture, all start dates are " 
            S"calculated from \nthe first Sunday in April, based on " 
            S"a standard set in 1986. For \ndates prior to 1986, " 
            S"the calculated start date may not be accurate." );
    }

    Console::WriteLine( S"\nLocal time: {0}\n", 
        localZone->StandardName );

    Console::WriteLine( headFmt, S"Year", S"Start", 
        S"End", S"Change" );
    Console::WriteLine( headFmt, S"----", S"-----", 
        S"---", S"------" );

    CreateDaylightTime( 1960, localZone );
    CreateDaylightTime( 1970, localZone );
    CreateDaylightTime( 1980, localZone );
    CreateDaylightTime( 1990, localZone );
    CreateDaylightTime( 2000, localZone );
    CreateDaylightTime( 2001, localZone );
    CreateDaylightTime( 2002, localZone );
    CreateDaylightTime( 2003, localZone );
    CreateDaylightTime( 2004, localZone );
    CreateDaylightTime( 2005, localZone );
    CreateDaylightTime( 2020, localZone );
    CreateDaylightTime( 2040, localZone );
} 

/*
This example of TimeZone::GetDaylightChanges( int ) generates the
following output, which varies depending on the time zone in which
it is run. The example creates DaylightTime objects for specified
years and displays the start and end dates and time change for
daylight saving time.

Note: In the [en-US] culture, all start dates are calculated from
the first Sunday in April, based on a standard set in 1986. For
dates prior to 1986, the calculated start date may not be accurate.

Local time: Pacific Standard Time

Year   Start               End                 Change
----   -----               ---                 ------
1960   1960-04-03 02:00    1960-10-30 02:00    01:00:00
1970   1970-04-05 02:00    1970-10-25 02:00    01:00:00
1980   1980-04-06 02:00    1980-10-26 02:00    01:00:00
1990   1990-04-01 02:00    1990-10-28 02:00    01:00:00
2000   2000-04-02 02:00    2000-10-29 02:00    01:00:00
2001   2001-04-01 02:00    2001-10-28 02:00    01:00:00
2002   2002-04-07 02:00    2002-10-27 02:00    01:00:00
2003   2003-04-06 02:00    2003-10-26 02:00    01:00:00
2004   2004-04-04 02:00    2004-10-31 02:00    01:00:00
2005   2005-04-03 02:00    2005-10-30 02:00    01:00:00
2020   2020-04-05 02:00    2020-10-25 02:00    01:00:00
2040   2040-04-01 02:00    2040-10-28 02:00    01:00:00
*/ 

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

See Also

TimeZone Class | TimeZone Members | System Namespace | Int32

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