DateTime.ToUniversalTime メソッド

定義

現在の DateTime オブジェクトの値を世界協定時刻 (UTC) に変換します。Converts the value of the current DateTime object to Coordinated Universal Time (UTC).

public:
 DateTime ToUniversalTime();
public DateTime ToUniversalTime ();
member this.ToUniversalTime : unit -> DateTime
Public Function ToUniversalTime () As DateTime

戻り値

Kind プロパティが Utc であるオブジェクト。通常は、現在の DateTime オブジェクトと等価な UTC が値として格納されます。ただし、変換後の値が MaxValue オブジェクトで表現可能な範囲を超えている場合は DateTime の値が格納され、逆に変換後の値が MinValue オブジェクトで表現可能な範囲を下回る場合は DateTime が格納されます。An object whose Kind property is Utc, and whose value is the UTC equivalent to the value of the current DateTime object, or MaxValue if the converted value is too large to be represented by a DateTime object, or MinValue if the converted value is too small to be represented by a DateTime object.

ToUniversalTimeメソッドの例を次に示します。The following example demonstrates the ToUniversalTime method.

using namespace System;

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

   DateTime localDateTime, univDateTime;
   try
   {
      localDateTime = DateTime::Parse(strDateTime);
      univDateTime = localDateTime.ToUniversalTime();
    
      Console::WriteLine("{0} local time is {1} universal time.",
                         localDateTime, univDateTime );
   }
   catch (FormatException^) 
   {
      Console::WriteLine("Invalid format.");
      return;
   }

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

   try
   {
      univDateTime = DateTime::Parse(strDateTime);
      localDateTime = univDateTime.ToLocalTime();
  
      Console::WriteLine("{0} universal time is {1} local time.",
                         univDateTime, localDateTime );
   }
   catch (FormatException^) 
   {
      Console::WriteLine("Invalid format.");
      return;
   }
}
// The example displays output like the following when run on a 
// computer whose culture is en-US in the Pacific Standard Time zone:
//     Enter a date and time.
//     12/10/2015 6:18 AM
//     12/10/2015 6:18:00 AM local time is 12/10/2015 2:18:00 PM universal time.
//     Enter a date and time in universal time.
//     12/20/2015 6:42:00
//     12/20/2015 6:42:00 AM universal time is 12/19/2015 10:42:00 PM local time.
using System;

class Example
{
    static void Main()
    {
        DateTime localDateTime, univDateTime;
        
        Console.WriteLine("Enter a date and time.");
        string strDateTime = Console.ReadLine();

        try {
            localDateTime = DateTime.Parse(strDateTime);
            univDateTime = localDateTime.ToUniversalTime();
    
            Console.WriteLine("{0} local time is {1} universal time.",
                                localDateTime,
                                    univDateTime); 
        }
        catch (FormatException) {
            Console.WriteLine("Invalid format.");
            return;
        }

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

        try {
            univDateTime = DateTime.Parse(strDateTime);
            localDateTime = univDateTime.ToLocalTime();
    
            Console.WriteLine("{0} universal time is {1} local time.",
                                     univDateTime,
                                     localDateTime); 
        }
        catch (FormatException) {
            Console.WriteLine("Invalid format.");
            return;
        }

    }
}
// The example displays output like the following when run on a 
// computer whose culture is en-US in the Pacific Standard Time zone:
//     Enter a date and time.
//     12/10/2015 6:18 AM
//     12/10/2015 6:18:00 AM local time is 12/10/2015 2:18:00 PM universal time.
//     Enter a date and time in universal time.
//     12/20/2015 6:42:00
//     12/20/2015 6:42:00 AM universal time is 12/19/2015 10:42:00 PM local time.
Module Example
    Sub Main()
      Dim localDateTime, univDateTime As DateTime
      
      Console.WriteLine("Enter a date and time.")
      Dim strDateTime As String = Console.ReadLine()
      Try
         localDateTime = DateTime.Parse(strDateTime)
         univDateTime = localDateTime.ToUniversalTime()
         Console.WriteLine("{0} local time is {1} universal time.", 
                           localDateTime, univDateTime)
      Catch exp As FormatException
         Console.WriteLine("Invalid format.")
      End Try

      Console.WriteLine("Enter a date and time in universal time.")
      strDateTime = Console.ReadLine()
      Try
         univDateTime = DateTime.Parse(strDateTime)
         localDateTime = univDateTime.ToLocalTime()
  
         Console.WriteLine("{0} universal time is {1} local time.", _
                           univDateTime, localDateTime)
      Catch exp As FormatException
         Console.WriteLine("Invalid format.")
      End Try
    End Sub
End Module
' The example displays output like the following when run on a 
' computer whose culture is en-US in the Pacific Standard Time zone:
'     Enter a date and time.
'     12/10/2015 6:18 AM
'     12/10/2015 6:18:00 AM local time is 12/10/2015 2:18:00 PM universal time.
'     Enter a date and time in universal time.
'     12/20/2015 6:42:00
'     12/20/2015 6:42:00 AM universal time is 12/19/2015 10:42:00 PM local time.

次の例では、SpecifyKind メソッドを使用して、Kind プロパティが ToLocalTime および ToUniversalTime の変換メソッドにどのように影響するかを示します。The following example uses the SpecifyKind method to demonstrate how the Kind property influences the ToLocalTime and ToUniversalTime conversion methods.

// 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

*/

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

'
'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
'

注釈

世界協定時刻 (UTC) は、現地時刻から UTC オフセットを差し引いた値に相当します。The Coordinated Universal Time (UTC) is equal to the local time minus the UTC offset. UTC オフセットの詳細については、「TimeZone.GetUtcOffset」を参照してください。For more information about the UTC offset, see TimeZone.GetUtcOffset. 変換では、現在の DateTime オブジェクトで表される時間に適用される夏時間ルールも考慮されます。The conversion also takes into account the daylight saving time rule that applies to the time represented by the current DateTime object.

重要

Windows XPWindows XP システムでは、ToUniversalTime メソッドは、現地時刻から UTC に変換するときに現在の調整規則のみを認識します。On Windows XPWindows XP systems, the ToUniversalTime method recognizes only the current adjustment rule when converting from local time to UTC. その結果、現在の調整規則が適用される前の期間の変換によって、現地時刻と UTC の差が正確に反映されない場合があります。As a result, conversions for periods before the current adjustment rule came into effect may not accurately reflect the difference between local time and UTC.

.NET Framework バージョン2.0 以降では、ToUniversalTime メソッドによって返される値は、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。Starting with the .NET Framework version 2.0, the value returned by the ToUniversalTime method is determined by the Kind property of the current DateTime object. 次の表では、考えられる結果について説明します。The following table describes the possible results.

種類Kind 結果Results
Utc 変換は実行されません。No conversion is performed.
Local 現在の DateTime オブジェクトは UTC に変換されます。The current DateTime object is converted to UTC.
Unspecified 現在の DateTime オブジェクトは、現地時刻であると見なされ、KindLocalているかのように変換されます。The current DateTime object is assumed to be a local time, and the conversion is performed as if Kind were Local.

注意

ToUniversalTime メソッドは、DateTime 値を現地時刻から UTC に変換します。The ToUniversalTime method converts a DateTime value from local time to UTC. ローカル以外のタイムゾーンの時刻を UTC に変換するには、TimeZoneInfo.ConvertTimeToUtc(DateTime, TimeZoneInfo) メソッドを使用します。To convert the time in a non-local time zone to UTC, use the TimeZoneInfo.ConvertTimeToUtc(DateTime, TimeZoneInfo) method. UTC からのオフセットがわかっている時刻を変換するには、ToUniversalTime メソッドを使用します。To convert a time whose offset from UTC is known, use the ToUniversalTime method.

日付と時刻のインスタンスの値があいまいな時刻の場合、このメソッドは標準時であると想定します。If the date and time instance value is an ambiguous time, this method assumes that it is a standard time. (あいまいな時刻とは、標準時またはローカルタイムゾーンの夏時間にマップできる時間です)。日付と時刻のインスタンスの値が無効な時刻の場合、このメソッドは単にローカルタイムゾーンの UTC オフセットから現地時刻を減算して、UTC を返します。(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 the date and time instance value is an invalid time, this method simply subtracts the local time from the local time zone's UTC offset to return UTC. (無効な時刻とは、夏時間調整規則の適用によって存在しない時刻です)。(An invalid time is one that does not exist because of the application of daylight saving time adjustment rules.)

注意 (呼び出し元)

ToUniversalTime() メソッドは、現地時刻を UTC に変換するために使用されることがあります。The ToUniversalTime() method is sometimes used to convert a local time to UTC. 次に、ToLocalTime() メソッドを呼び出して、元のローカル時刻を復元します。The ToLocalTime() method is then called to restore the original local time. ただし、元の時刻がローカルタイムゾーンの無効な時刻を表している場合、2つのローカル時刻値は等しくなりません。However, if the original time represents an invalid time in the local time zone, the two local time values will not be equal. 詳細と例については、ToLocalTime() メソッドを参照してください。For additional information and an example, see the ToLocalTime() method.

Windows XPWindows XP システムでは、ToUniversalTime() メソッドはローカルタイムゾーンの現在の調整規則のみを認識します。これは、ダウンレベルの日付 (つまり、現在の調整規則の開始日よりも前の日付) を含むすべての日付に適用されます。On Windows XPWindows XP systems, the ToUniversalTime() method recognizes only the current adjustment rule for the local time zone, which it applies to all dates, including down-level dates (that is, dates that are earlier than the starting date of the current adjustment rule). ローカルの日付と時刻の計算を正確に行う必要がある Windows XPWindows XP で実行されているアプリケーションは、FindSystemTimeZoneById(String) メソッドを使用して、ローカルタイムゾーンに対応する TimeZoneInfo オブジェクトを取得し、その ConvertTimeToUtc(DateTime, TimeZoneInfo) メソッドを呼び出すことで、この動作を回避する必要があります。Applications running on Windows XPWindows XP that require historically accurate local date and time calculations must work around this behavior by using the FindSystemTimeZoneById(String) method to retrieve a TimeZoneInfo object that corresponds to the local time zone and calling its ConvertTimeToUtc(DateTime, TimeZoneInfo) method.

次の例では、米国太平洋標準時タイムゾーンの Windows XPWindows XP システムの ToUniversalTime()ConvertTimeToUtc(DateTime, TimeZoneInfo) のメソッドの違いを示します。The following example illustrates the difference between the ToUniversalTime() and ConvertTimeToUtc(DateTime, TimeZoneInfo) methods on a Windows XPWindows XP system in the U.S. Pacific Time zone. 最初の2つのメソッド呼び出しでは、現在のタイムゾーン調整規則 (2007 で有効になっていた) が2006の日付に適用されます。The first two method calls apply the current time zone adjustment rule (which went into effect in 2007) to a date in 2006. 現在の調整規則では、3月の第2日曜日に夏時間への移行を行います。2006で有効になった前のルールは、4月の最初の日曜日に夏時間への移行を行うために提供されています。The current adjustment rule provides for the transition to daylight saving time on the second Sunday of March; the previous rule, which was in effect in 2006, provided for the transition to daylight saving time to occur on the first Sunday of April. 3番目のメソッド呼び出しでのみ、この履歴日時の変換が正確に実行されます。Only the third method call accurately performs this historical date and time conversion.

[! code-csharpToUniversalTime # 1][! code-vbToUniversalTime # 1][!code-csharpSystem.DateTime.ToUniversalTime#1] [!code-vbSystem.DateTime.ToUniversalTime#1]

適用対象

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