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TimeZone.ToUniversalTime Method

Returns the coordinated universal time (UTC) that corresponds to a specified local time.

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

'Declaration
Public Overridable Function ToUniversalTime ( _
	time As DateTime _
) As DateTime
'Usage
Dim instance As TimeZone
Dim time As DateTime
Dim returnValue As DateTime

returnValue = instance.ToUniversalTime(time)
public DateTime ToUniversalTime (
	DateTime time
)
public function ToUniversalTime (
	time : DateTime
) : DateTime

Parameters

time

The local date and time.

Return Value

A DateTime instance whose value is the UTC time that corresponds to time.

Coordinated universal time (UTC) was previously known as Greenwich Mean Time (GMT). Local time is the date and time on the computer you are using. Offset is the difference between local time and UTC. That is:

UTC = local time - offset

The following code example uses the ToUniversalTime method to return the Coordinated Universal Times (UTC) that correspond to selected local times.

' Example of the TimeZone.IsDaylightSavingTime( DateTime ),
' TimeZone.IsDaylightSavingTime( DateTime, DaylightTime ), and 
' TimeZone.ToUniversalTime( DateTime ) methods.
Imports System
Imports System.Globalization
Imports Microsoft.VisualBasic

Module DaylightTimeDemo

    Sub Main( )

        Const headFmt As String = "{0,-22}{1,-10}{2,-10}{3,-10}{4}"

        ' Get the local time zone and a base local time.
        Dim localZone As TimeZone = TimeZone.CurrentTimeZone
        Dim localTime As DateTime = new DateTime( 2001, 1, 1 )

        Console.WriteLine( "This example of " & vbCrLf & _
            "   TimeZone.IsDaylightSavingTime( DateTime ), " & _
            vbCrLf & "   TimeZone.IsDaylightSavingTime( " & _
            "DateTime, DaylightTime ), and " & vbCrLf & _
            "   TimeZone.ToUniversalTime( DateTime )" & vbCrLf & _
            "generates the following output, which varies " & _
            "depending on the " & vbCrLf & "time zone in which " & _
            "it is run." & vbCrLf )
        Console.WriteLine( "The example creates " & _
            "several local times and the corresponding " & vbCrLf & _
            "Coordinated Universal Times (UTC) and shows if " & _
            "they occur in " & vbCrLf & "daylight saving time " & _
            "(DST), both for specified years and for " & vbCrLf & _
            "any year." & vbCrLf )
        Console.WriteLine( "Local time: {0}" & vbCrLf, _
            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.
        Dim daylight2001 As DaylightTime = _
            localZone.GetDaylightChanges( 2001 )
        Dim daylight2002 As DaylightTime = _
            localZone.GetDaylightChanges( 2002 )

        ' Generate several local times.
        Dim loopX As Integer
        For loopX = 0 to 10

            ' Calculate the corresponding UTC.
            Dim utcTime As DateTime = _
                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 )
        Next loopX
    End Sub
End Module 

' 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

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

class DaylightTimeDemo
{
    public static void main(String[] args)
    {
        final String headFmt = "{0,-22}{1,-10}{2,-10}{3,-10}{4}";

        // Get the local time zone and a base local time.
        TimeZone localZone = TimeZone.get_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.get_StandardName());
        Console.WriteLine(headFmt, new Object[] { 
            "Local Date and Time", "2001 DST?", "2002 DST?", "Any DST?",
            "Corresponding UTC" });
        Console.WriteLine(headFmt, new Object[] { "-------------------",
            "---------", "---------", "--------", "-----------------" });

        // 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}", new Object[]
                { localTime, (System.Boolean)TimeZone.IsDaylightSavingTime(
                localTime, daylight2001), (System.Boolean)
                TimeZone.IsDaylightSavingTime(localTime, daylight2002),
                (System.Boolean)localZone.IsDaylightSavingTime
                (localTime), utcTime });

            // Advance to another local time.
            localTime = localTime.AddDays(109.1);
        }
    } //main
} //DaylightTimeDemo

/*
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 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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