DateTime.ToLocalTime DateTime.ToLocalTime DateTime.ToLocalTime DateTime.ToLocalTime Method

定义

将当前 DateTime 对象的值转换为本地时间。Converts the value of the current DateTime object to local time.

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

返回

一个对象,其 Kind 属性为 Local,并且其值为等效于当前 DateTime 对象的值的本地时间;如果经转换的值过大以至于不能由 MaxValue 对象表示,则为 DateTime,或者,如果经转换的值过小以至于不能表示为 MinValue 对象,则为 DateTimeAn object whose Kind property is Local, and whose value is the local time 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 as a DateTime object.

示例

下面的示例演示 ToLocalTime 方法。The following example demonstrates the ToLocalTime method. 请注意,准确的输出取决于当前区域性以及运行它的系统的本地时区。Note that the exact output depends on the current culture and the local time zone of the system on which it is run.

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.

下面的示例使用 SpecifyKind 方法来演示 @no__t 的属性如何影响 @no__t 和 @no__t 转换方法。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
'

注解

本地时间等于协调世界时(UTC)时间加上 UTC 偏移量。The local time is equal to the Coordinated Universal Time (UTC) time plus the UTC offset. 有关 UTC 偏移量的详细信息,请参阅 TimeZone.GetUtcOffsetFor more information about the UTC offset, see TimeZone.GetUtcOffset. 该转换还会考虑适用于当前 @no__t 0 对象所表示的时间的夏令时规则。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 系统上,第 1 @no__t 方法仅在将 UTC 转换为本地时间时才识别当前调整规则。On Windows XPWindows XP systems, the ToLocalTime method recognizes only the current adjustment rule when converting from UTC to local time. 因此,当前调整规则生效前的时间转换可能无法准确反映 UTC 与本地时间之间的差异。As a result, conversions for periods before the current adjustment rule came into effect may not accurately reflect the difference between UTC and local time.

从 .NET Framework 版本2.0 开始,ToLocalTime 方法返回的值由当前 @no__t 2 对象的 Kind 属性确定。Starting with the .NET Framework version 2.0, the value returned by the ToLocalTime method is determined by the Kind property of the current DateTime object. 下表描述了可能的结果。The following table describes the possible results.

类型Kind 结果Results
Utc 此 @no__t 的实例将转换为本地时间。This instance of DateTime is converted to local time.
Local 不执行任何转换。No conversion is performed.
Unspecified 此 @no__t 的实例假定为 UTC 时间,并且执行转换的方式与 Kind Utc 一样。This instance of DateTime is assumed to be a UTC time, and the conversion is performed as if Kind were Utc.

备注

@No__t-0 方法将 @no__t 值从 UTC 转换为本地时间。The ToLocalTime method converts a DateTime value from UTC to local time. 若要将任何指定时区中的时间转换为本地时间,请使用 TimeZoneInfo.ConvertTime 方法。To convert the time in any designated time zone to local time, use the TimeZoneInfo.ConvertTime method.

转换返回的值是 DateTime,其 @no__t 属性始终返回 LocalThe value returned by the conversion is a DateTime whose Kind property always returns Local. 因此,即使对同一 @no__t @no__t 重复应用了0,也会返回有效的结果。Consequently, a valid result is returned even if ToLocalTime is applied repeatedly to the same DateTime.

调用方说明

您可以使用 ToLocalTime() 方法来还原已通过 @no__t 或 FromFileTimeUtc(Int64) 方法转换为 UTC 的本地日期和时间值。You can use the ToLocalTime() method to restore a local date and time value that was converted to UTC by the ToUniversalTime() or FromFileTimeUtc(Int64) method. 但是,如果原始时间表示本地时区中的无效时间,则它将不与还原的值匹配。However, if the original time represents an invalid time in the local time zone, it will not match the restored value. ToLocalTime() 方法将时间从 UTC 转换为本地时区时,它还会调整时间,以便在本地时区中有效。When the ToLocalTime() method converts a time from UTC to the local time zone, it also adjusts the time so that is valid in the local time zone.

例如,从标准时间转换为夏时制发生在美国太平洋时区于2010年3月14日上午2:00 点,时间前进一小时,上午3:00For example, the transition from standard time to daylight saving time occurs in the U.S. Pacific Time zone on March 14, 2010, at 2:00 A.M., when the time advances by one hour, to 3:00 A.M. 此小时间隔为无效时间,即此时区中不存在的时间间隔。This hour interval is an invalid time, that is, a time interval that does not exist in this time zone. 下面的示例显示,当处于此范围内的时间由 ToUniversalTime() 方法转换为 UTC,然后通过 ToLocalTime() 方法还原时,原始值将调整为有效时间。The following example shows that when a time that falls within this range is converted to UTC by the ToUniversalTime() method and is then restored by the ToLocalTime() method, the original value is adjusted to become a valid time. 如示例所示,您可以通过将特定日期和时间值传递到 IsInvalidTime(DateTime) 方法来确定是否可以修改该日期和时间值。You can determine whether a particular date and time value may be subject to modification by passing it to the IsInvalidTime(DateTime) method, as the example illustrates.

[!code-csharpSystem.DateTime.ToLocalTime#1] [!code-vbSystem.DateTime.ToLocalTime#1][!code-csharpSystem.DateTime.ToLocalTime#1] [!code-vbSystem.DateTime.ToLocalTime#1]

适用于

另请参阅