共用方式為


DateTime.ToLocalTime 方法

定義

將目前 DateTime 物件的值轉換成本地時間。

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

傳回

Kind屬性為 Local 的物件,如果轉換的值太大而無法以物件表示,則其值為相當於目前 DateTime 物件的當地時間,或者如果轉換的值太大而無法由 DateTime 物件表示 DateTime ,則為DateTime.MinValue

範例

下列範例示範 ToLocalTime 方法。 請注意,確切的輸出取決於目前文化特性及其執行所在系統的當地時區。

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.
open System

printfn "Enter a date and time."

try
    let strDateTime = stdin.ReadLine()
    let localDateTime = DateTime.Parse strDateTime
    let univDateTime = localDateTime.ToUniversalTime()

    printfn $"{localDateTime} local time is {univDateTime} universal time."

with :? FormatException ->
    printfn "Invalid format."

printfn "Enter a date and time in universal time."

try
    let strDateTime = stdin.ReadLine()
    let univDateTime = DateTime.Parse strDateTime
    let localDateTime = univDateTime.ToLocalTime()

    printfn $"{univDateTime} universal time is {localDateTime} local time."

with :? FormatException ->
    printfn "Invalid format."

// 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.

下列範例會 SpecifyKind 使用 方法來示範 屬性 ToLocalTime 如何影響 KindToUniversalTime 轉換方法。

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

open System

// 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.

let datePatt = @"M/d/yyyy hh:mm:ss tt"

let display title (inputDt: DateTime) =
    // Display the original DateTime.

    let dispDt = inputDt
    let dtString = dispDt.ToString datePatt
    printfn $"%s{title} {dtString}, Kind = {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.

    let dispDt = inputDt.ToLocalTime()
    let dtString = dispDt.ToString datePatt
    printfn $"  ToLocalTime:     {dtString}, Kind = {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.

    let dispDt = inputDt.ToUniversalTime()
    let dtString = dispDt.ToString datePatt
    printfn $"  ToUniversalTime: {dtString}, Kind = {dispDt.Kind}\n" 

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

let displayNow title (inputDt: DateTime) =
    let dtString = inputDt.ToString datePatt
    printfn $"%s{title} {dtString}, Kind = {inputDt.Kind}"

[<EntryPoint>]
let main _ =

    // Get the date and time for the current moment, adjusted
    // to the local time zone.

    let saveNow = DateTime.Now

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

    let saveUtcNow = DateTime.UtcNow

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

    displayNow "UtcNow: .........." saveUtcNow
    displayNow "Now: ............." saveNow
    printfn ""

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

    let myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Utc)
    display "Utc: ............." myDt

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

    let myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Local)
    display "Local: ..........." myDt

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

    let myDt = DateTime.SpecifyKind(saveNow, DateTimeKind.Unspecified)
    display "Unspecified: ....." myDt

    0


// 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

*/

' 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
'

備註

當地時間等於國際標準時間 (UTC) 時間加上 UTC 位移。 如需 UTC 位移的詳細資訊,請參閱 TimeZoneInfo.GetUtcOffset 。 轉換也會考慮套用至目前 DateTime 物件所代表時間的日光節約時間規則。

重要

在 Windows XP 系統上, ToLocalTime 此方法只會在從 UTC 轉換為當地時間時辨識目前的調整規則。 因此,目前調整規則生效之前的期間轉換可能無法精確地反映 UTC 與當地時間之間的差異。

從 .NET Framework 2.0 版開始,方法傳 ToLocalTime 回的值取決於 Kind 目前 DateTime 物件的 屬性。 下表描述可能的結果。

種類 結果
Utc 這個 的實例 DateTime 會轉換成當地時間。
Local 不會執行任何轉換。
Unspecified 這個 的實例 DateTime 假設為 UTC 時間,而且轉換的執行方式就像 KindUtc 一樣。

注意

方法會將 ToLocalTimeDateTime 值從 UTC 轉換為當地時間。 若要將任何指定時區中的時間轉換為當地時間,請使用 TimeZoneInfo.ConvertTime 方法。

轉換傳回的值是 DateTime ,其 Kind 屬性一律會傳 Local 回 。 因此,即使 ToLocalTime 重複套用至相同的 DateTime ,也會傳回有效的結果。

給呼叫者的注意事項

您可以使用 ToLocalTime() 方法來還原 或 FromFileTimeUtc(Int64) 方法轉換成 UTC ToUniversalTime() 的本機日期和時間值。 不過,如果原始時間代表當地時區中的無效時間,它就不會符合還原的值。 ToLocalTime()當 方法將時間從 UTC 轉換為當地時區時,也會調整時間,以便在當地時區中有效。

例如,從標準時間到日光節約時間的轉換發生在美國太平洋時區 2010 年 3 月 14 日,上午 2:00,時間在上午 2:00 到上午 3:00。這個小時間隔是不正確時間,也就是這個時區中不存在的時間間隔。 下列範例顯示,當屬於這個範圍的時間由 方法轉換成 UTC ToUniversalTime() ,然後由 ToLocalTime() 方法還原時,原始值會調整為成為有效的時間。 您可以藉由將特定日期和時間值傳遞至 IsInvalidTime(DateTime) 方法來判斷特定日期和時間值是否可能受到修改,如範例所示。

using System;

public class Example
{
   public static void Main()
   {
      DateTime date1 = new DateTime(2010, 3, 14, 2, 30, 0, DateTimeKind.Local);
      Console.WriteLine("Invalid time: {0}",
                        TimeZoneInfo.Local.IsInvalidTime(date1));
      DateTime utcDate1 = date1.ToUniversalTime();
      DateTime date2 = utcDate1.ToLocalTime();
      Console.WriteLine("{0} --> {1}", date1, date2);
   }
}
// The example displays the following output:
//       Invalid time: True
//       3/14/2010 2:30:00 AM --> 3/14/2010 3:30:00 AM
open System

let date1 = DateTime(2010, 3, 14, 2, 30, 0, DateTimeKind.Local)
printfn $"Invalid time: {TimeZoneInfo.Local.IsInvalidTime date1}"
let utcDate1 = date1.ToUniversalTime()
let date2 = utcDate1.ToLocalTime()
printfn $"{date1} --> {date2}"

// The example displays the following output:
//       Invalid time: True
//       3/14/2010 2:30:00 AM --> 3/14/2010 3:30:00 AM
Module Example
   Public Sub Main()
      Dim date1 As New Date(2010, 3, 14, 2, 30, 0, DateTimeKind.Local)
      Console.WriteLine("Invalid time: {0}", _
                        TimeZoneInfo.Local.IsInvalidTime(date1))
      Dim utcDate1 As Date = date1.ToUniversalTime()
      Dim date2 As Date = utcDate1.ToLocalTime()
      Console.WriteLine("{0} --> {1}", date1, date2)      
   End Sub
End Module
' The example displays the following output:
'       Invalid time: True
'       3/14/2010 2:30:00 AM --> 3/14/2010 3:30:00 AM

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