DateTime.ToLocalTime メソッドとは何？わかりやすく解説 Weblio辞書

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DateTime.ToLocalTime メソッド

現在の DateTime オブジェクトの値を現地時刻に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Function ToLocalTime As
 DateTime

Visual Basic (使用法)

Dim instance As DateTime
Dim returnValue As DateTime

returnValue = instance.ToLocalTime

public DateTime ToLocalTime ()

C++

public:
DateTime ToLocalTime ()

public DateTime ToLocalTime ()

JScript

public function ToLocalTime () : DateTime

戻り値
Kind プロパティが Local の DateTime オブジェクト。通常は、現在の DateTime オブジェクトと等価な現地時刻が値として格納されます。ただし、変換後の値が DateTime オブジェクトで表現可能な範囲を超えている場合は MaxValue の値が、逆に DateTime オブジェクトで表現可能な範囲を下回る場合は MinValue が格納されます。

解説

現在時刻は、UTC 時刻に UTC オフセットを加算した値です。UTC オフセットの詳細については、TimeZone.GetUtcOffset のトピックを参照してください。また、変換時には、現在の DateTime オブジェクトが表す時刻に適用される夏時間も考慮されます。

.NET Framework Version 2.0 以降では、ToLocalTime メソッドの戻り値は、現在の DateTime オブジェクトの Kind プロパティによって決定されます。Kind プロパティの値によって、実行結果にどのような違いが生じるかを次の表に示します。

Kind プロパティの値	結果
Utc	DateTime のインスタンスが現地時刻に変換されます。
Local	変換は実行されません。
Unspecified	DateTime のインスタンスが UTC 時刻ベースであるものと見なされ、Kind が Utc の場合と同じ変換結果になります。

変換によって得られる値は、Kind プロパティが常に Local を返すような DateTime になります。したがって、同じ DateTime に対して、繰り返し ToLocalTime を適用しても、有効な結果が返されます。

このメソッドは、計算するときに常にローカルタイムゾーンを使用します。

使用例

ToLocalTime メソッドのコード例を次に示します。

Visual Basic

System.Console.WriteLine("Enter a date and time.")
Dim strDateTime As String
strDateTime = System.Console.ReadLine()

Dim localDateTime As System.DateTime
Try
   localDateTime = System.DateTime.Parse(strDateTime)
Catch exp As System.FormatException
   System.Console.WriteLine("Invalid format.")
End Try

Dim univDateTime As System.DateTime
univDateTime = localDateTime.ToUniversalTime()

System.Console.WriteLine("{0} local time is {1} universal time.",
 _
                           localDateTime, _
                           univDateTime)

System.Console.WriteLine("Enter a date and time in universal time.")
strDateTime = System.Console.ReadLine()

Try
   univDateTime = System.DateTime.Parse(strDateTime)
Catch exp As System.FormatException
   System.Console.WriteLine("Invalid format.")
End Try

localDateTime = univDateTime.ToLocalTime()

System.Console.WriteLine("{0} universal time is {1} local time.",
 _
                           univDateTime, _
                           localDateTime)

System.Console.WriteLine("Enter a date and time.");
string strDateTime = System.Console.ReadLine();

System.DateTime localDateTime;
try {
    localDateTime = System.DateTime.Parse(strDateTime);
}
catch (System.FormatException) {
    System.Console.WriteLine("Invalid format.");
    return;
}

System.DateTime univDateTime = localDateTime.ToUniversalTime();

System.Console.WriteLine("{0} local time is {1} universal time.",
                         localDateTime,
                         univDateTime); 

System.Console.WriteLine("Enter a date and time in universal
 time.");
strDateTime = System.Console.ReadLine();

try {
    univDateTime = System.DateTime.Parse(strDateTime);
}
catch (System.FormatException) {
    System.Console.WriteLine("Invalid format.");
    return;
}

localDateTime = univDateTime.ToLocalTime();

System.Console.WriteLine("{0} universal time is {1} local time.",
                         univDateTime,
                         localDateTime);

C++

System::Console::WriteLine( "Enter a date and time." );
String^ strDateTime = System::Console::ReadLine();

System::DateTime localDateTime;
try
{
   localDateTime = System::DateTime::Parse( strDateTime );
}
catch ( System::FormatException^ ) 
{
   System::Console::WriteLine( "Invalid format." );
   return;
}

System::DateTime univDateTime = localDateTime.ToUniversalTime();

System::Console::WriteLine( "{0} local time is {1} universal time.",
   localDateTime, univDateTime );

System::Console::WriteLine( "Enter a date and time in universal
 time." );
strDateTime = System::Console::ReadLine();

try
{
   univDateTime = System::DateTime::Parse( strDateTime );
}
catch ( System::FormatException^ ) 
{
   System::Console::WriteLine( "Invalid format." );
   return;
}

localDateTime = univDateTime.ToLocalTime();

System::Console::WriteLine( "{0} universal time is {1} local time.",
   univDateTime, localDateTime );

System.Console.WriteLine("Enter a date and time.");
String strDateTime = System.Console.ReadLine();

System.DateTime localDateTime;
try {
    localDateTime = System.DateTime.Parse(strDateTime);
}
catch (System.FormatException exp) {
    System.Console.WriteLine("Invalid format.");
    return;
}
System.DateTime univDateTime = localDateTime.ToUniversalTime();
System.Console.WriteLine("{0} local time is {1} universal time.", 
    localDateTime, univDateTime);
System.Console.WriteLine("Enter a date and time in universal
 time.");
strDateTime = System.Console.ReadLine();
try {
    univDateTime = System.DateTime.Parse(strDateTime);
}
catch (System.FormatException exp) {
    System.Console.WriteLine("Invalid format.");
    return;
}
localDateTime = univDateTime.ToLocalTime();
System.Console.WriteLine("{0} universal time is {1} local time.", 
    univDateTime, localDateTime);

次のコード例では、Kind プロパティが ToLocalTime と ToUniversalTime の 2 つの変換メソッドに与える影響を、SpecifyKind メソッドを使って示しています。

Visual Basic

' This code example demonstrates the DateTime Kind, Now, and
' UtcNow properties, and the SpecifyKind(), ToLocalTime(), 
' and ToUniversalTime() methods.
Imports System

Class Sample
    Public Shared Sub Main()
 
        ' Get the date and time for the current moment, adjusted 
        ' to the local time zone.
        Dim saveNow As DateTime = DateTime.Now
        
        ' Get the date and time for the current moment expressed 
        ' as coordinated universal time (UTC).
        Dim saveUtcNow As DateTime = DateTime.UtcNow
        Dim myDt As DateTime
        
        ' Display the value and Kind property of the current moment
 
        ' expressed as UTC and local time.
        DisplayNow("UtcNow: ..........", saveUtcNow)
        DisplayNow("Now: .............", saveNow)
        Console.WriteLine()
        
        ' Change the Kind property of the current moment to 
        ' DateTimeKind.Utc and display the result.
        myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Utc)
        Display("Utc: .............", myDt)
        
        ' Change the Kind property of the current moment to 
        ' DateTimeKind.Local and display the result.
        myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Local)
        Display("Local: ...........", myDt)
        
        ' Change the Kind property of the current moment to 
        ' DateTimeKind.Unspecified and display the result.
        myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Unspecified)
        Display("Unspecified: .....", myDt)
    End Sub 'Main
    
    ' Display the value and Kind property of a DateTime structure, the
 
    ' DateTime structure converted to local time, and the DateTime 
    ' structure converted to universal time. 

    Public Shared datePatt As
 String = "M/d/yyyy hh:mm:ss tt"
    
    Public Shared Sub Display(ByVal
 title As String, ByVal
 inputDt As DateTime) 
        Dim dispDt As DateTime = inputDt
        Dim dtString As String
        
        ' Display the original DateTime.
        dtString = dispDt.ToString(datePatt)
        Console.WriteLine("{0} {1}, Kind = {2}", title,
 dtString, dispDt.Kind)
        
        ' Convert inputDt to local time and display the result. 
        ' If inputDt.Kind is DateTimeKind.Utc, the conversion is performed.
        ' If inputDt.Kind is DateTimeKind.Local, the conversion is not
 performed.
        ' If inputDt.Kind is DateTimeKind.Unspecified, the conversion
 is 
        ' performed as if inputDt was universal time.
        dispDt = inputDt.ToLocalTime()
        dtString = dispDt.ToString(datePatt)
        Console.WriteLine("  ToLocalTime:     {0}, Kind = {1}",
 dtString, dispDt.Kind)
        
        ' Convert inputDt to universal time and display the result.
 
        ' If inputDt.Kind is DateTimeKind.Utc, the conversion is not
 performed.
        ' If inputDt.Kind is DateTimeKind.Local, the conversion is performed.
        ' If inputDt.Kind is DateTimeKind.Unspecified, the conversion
 is 
        ' performed as if inputDt was local time.
        dispDt = inputDt.ToUniversalTime()
        dtString = dispDt.ToString(datePatt)
        Console.WriteLine("  ToUniversalTime: {0}, Kind = {1}",
 dtString, dispDt.Kind)
        Console.WriteLine()
    End Sub 'Display
    
    
    ' Display the value and Kind property for DateTime.Now and DateTime.UtcNow.

    Public Shared Sub DisplayNow(ByVal
 title As String, ByVal
 inputDt As DateTime) 
        Dim dtString As String
 = inputDt.ToString(datePatt)
        Console.WriteLine("{0} {1}, Kind = {2}", title,
 dtString, inputDt.Kind)
    End Sub 'DisplayNow
End Class 'Sample

'
'This code example produces the following results:
'
'UtcNow: .......... 5/6/2005 09:34:42 PM, Kind = Utc
'Now: ............. 5/6/2005 02:34:42 PM, Kind = Local
'
'Utc: ............. 5/6/2005 02:34:42 PM, Kind = Utc
'  ToLocalTime:     5/6/2005 07:34:42 AM, Kind = Local
'  ToUniversalTime: 5/6/2005 02:34:42 PM, Kind = Utc
'
'Local: ........... 5/6/2005 02:34:42 PM, Kind = Local
'  ToLocalTime:     5/6/2005 02:34:42 PM, Kind = Local
'  ToUniversalTime: 5/6/2005 09:34:42 PM, Kind = Utc
'
'Unspecified: ..... 5/6/2005 02:34:42 PM, Kind = Unspecified
'  ToLocalTime:     5/6/2005 07:34:42 AM, Kind = Local
'  ToUniversalTime: 5/6/2005 09:34:42 PM, Kind = Utc
'

// This code example demonstrates the DateTime Kind, Now, and
// UtcNow properties, and the SpecifyKind(), ToLocalTime(), 
// and ToUniversalTime() methods.

using System;

class Sample 
{
    public static void Main()
 
    {
// Get the date and time for the current moment, adjusted 
// to the local time zone.

    DateTime saveNow = DateTime.Now;

// Get the date and time for the current moment expressed 
// as coordinated universal time (UTC).

    DateTime saveUtcNow = DateTime.UtcNow;
    DateTime myDt;

// Display the value and Kind property of the current moment 
// expressed as UTC and local time.

    DisplayNow("UtcNow: ..........", saveUtcNow);
    DisplayNow("Now: .............", saveNow);
    Console.WriteLine();

// Change the Kind property of the current moment to 
// DateTimeKind.Utc and display the result.

    myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Utc);
    Display("Utc: .............", myDt);

// Change the Kind property of the current moment to 
// DateTimeKind.Local and display the result.

    myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Local);
    Display("Local: ...........", myDt);

// Change the Kind property of the current moment to 
// DateTimeKind.Unspecified and display the result.

    myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Unspecified);
    Display("Unspecified: .....", myDt);
    }

// Display the value and Kind property of a DateTime structure, the
 
// DateTime structure converted to local time, and the DateTime 
// structure converted to universal time. 

    public static string
 datePatt = @"M/d/yyyy hh:mm:ss tt";
    public static void Display(string
 title, DateTime inputDt)
    {
    DateTime dispDt = inputDt;
    string dtString;

// Display the original DateTime.

    dtString = dispDt.ToString(datePatt);
    Console.WriteLine("{0} {1}, Kind = {2}", 
                      title, dtString, dispDt.Kind);

// Convert inputDt to local time and display the result. 
// If inputDt.Kind is DateTimeKind.Utc, the conversion is performed.
// If inputDt.Kind is DateTimeKind.Local, the conversion is not performed.
// If inputDt.Kind is DateTimeKind.Unspecified, the conversion is 
// performed as if inputDt was universal time.

    dispDt = inputDt.ToLocalTime();
    dtString = dispDt.ToString(datePatt);
    Console.WriteLine("  ToLocalTime:     {0}, Kind = {1}", 
                      dtString, dispDt.Kind);

// Convert inputDt to universal time and display the result. 
// If inputDt.Kind is DateTimeKind.Utc, the conversion is not performed.
// If inputDt.Kind is DateTimeKind.Local, the conversion is performed.
// If inputDt.Kind is DateTimeKind.Unspecified, the conversion is 
// performed as if inputDt was local time.

    dispDt = inputDt.ToUniversalTime();
    dtString = dispDt.ToString(datePatt);
    Console.WriteLine("  ToUniversalTime: {0}, Kind = {1}", 
                      dtString, dispDt.Kind);
    Console.WriteLine();
    }

// Display the value and Kind property for DateTime.Now and DateTime.UtcNow.

    public static void DisplayNow(string
 title, DateTime inputDt)
    {
    string dtString = inputDt.ToString(datePatt);
    Console.WriteLine("{0} {1}, Kind = {2}", 
                      title, dtString, inputDt.Kind);
    }
}

/*
This code example produces the following results:

UtcNow: .......... 5/6/2005 09:34:42 PM, Kind = Utc
Now: ............. 5/6/2005 02:34:42 PM, Kind = Local

Utc: ............. 5/6/2005 02:34:42 PM, Kind = Utc
  ToLocalTime:     5/6/2005 07:34:42 AM, Kind = Local
  ToUniversalTime: 5/6/2005 02:34:42 PM, Kind = Utc

Local: ........... 5/6/2005 02:34:42 PM, Kind = Local
  ToLocalTime:     5/6/2005 02:34:42 PM, Kind = Local
  ToUniversalTime: 5/6/2005 09:34:42 PM, Kind = Utc

Unspecified: ..... 5/6/2005 02:34:42 PM, Kind = Unspecified
  ToLocalTime:     5/6/2005 07:34:42 AM, Kind = Local
  ToUniversalTime: 5/6/2005 09:34:42 PM, Kind = Utc

*/

プラットフォーム

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

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
DateTime 構造体
DateTime メンバ
System 名前空間
TimeZone
GetUtcOffset
TimeZone.GetDaylightChanges
ToUniversalTime

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DateTime.ToLocalTime メソッドとは？わかりやすく解説