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IsDaylightSavingTime Method (DateTime, DaylightTime)

TimeZone.IsDaylightSavingTime Method (DateTime, DaylightTime)

Returns a value indicating whether the specified date and time is within the specified daylight saving time period.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public static bool IsDaylightSavingTime(
	DateTime time,
	DaylightTime daylightTimes
)

Parameters

time
Type: System.DateTime
A date and time.
daylightTimes
Type: System.Globalization.DaylightTime
A daylight saving time period.

Return Value

Type: System.Boolean
true if time is in daylightTimes; otherwise, false.

ExceptionCondition
ArgumentNullException

daylightTimes is null.

The TimeZoneInfo.IsDaylightSavingTime method provides the same functionality as this overload of the 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 a particular year.


// Example of the TimeZone.IsDaylightSavingTime( DateTime ),
// TimeZone.IsDaylightSavingTime( DateTime, DaylightTime ), and 
// TimeZone.ToUniversalTime( DateTime ) methods.
using System;
using System.Globalization;

class DaylightTimeDemo
{
    static void Main( )
    {
        const 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 = new 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
*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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