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DateTime.ToUniversalTime Method

Converts the value of the current DateTime object to Coordinated Universal Time (UTC).

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
public DateTime ToUniversalTime()

Return Value

Type: System.DateTime
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.

The Coordinated Universal Time (UTC) is equal to the local time minus the UTC offset. For more information about the UTC offset, see TimeZone.GetUtcOffset. The conversion also takes into account the daylight saving time rule that applies to the time represented by the current DateTime object.

Important noteImportant

   On Windows XP systems, the ToUniversalTime method recognizes only the current adjustment rule when converting from local time to UTC. 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. 

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. The following table describes the possible results.

Kind

Results

Utc

No conversion is performed.

Local

The current DateTime object is converted to UTC.

Unspecified

The current DateTime object is assumed to be a local time, and the conversion is performed as if Kind were Local.

NoteNote

The ToUniversalTime method converts a DateTime value from local time to UTC. To convert the time in a non-local time zone to UTC, use the TimeZoneInfo.ConvertTimeToUtc(DateTime, TimeZoneInfo) method. To convert a time whose offset from UTC is known, use the ToUniversalTime method.

If the date and time instance value is an ambiguous time, this method assumes that it is a standard time. (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. (An invalid time is one that does not exist because of the application of daylight saving time adjustment rules.)

Notes to Callers

The ToUniversalTime method is sometimes used to convert a local time to UTC. The ToLocalTime method is then called to restore the original local time. However, if the original time represents an invalid time in the local time zone, the two local time values will not be equal. For additional information and an example, see the ToLocalTime method.

On Windows 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). Applications running on Windows XP that require historically accurate local date and time calculations must work around this behavior by using the FindSystemTimeZoneById method to retrieve a TimeZoneInfo object that corresponds to the local time zone and calling its TimeZoneInfo.ConvertTimeToUtc(DateTime, TimeZoneInfo) method.

The following example illustrates the difference between the ToUniversalTime and TimeZoneInfo.ConvertTimeToUtc(DateTime, TimeZoneInfo) methods on a Windows XP system in the U.S. Pacific Time zone. The first two method calls apply the current time zone adjustment rule (which went into effect in 2007) to a date in 2006. 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. Only the third method call accurately performs this historical date and time conversion.


using System;

public class Example
{
   public static void Main()
   {
      DateTime date1 = new DateTime(2006, 3, 21, 2, 0, 0);

      Console.WriteLine(date1.ToUniversalTime());
      Console.WriteLine(TimeZoneInfo.ConvertTimeToUtc(date1));

      TimeZoneInfo tz = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");  
      Console.WriteLine(TimeZoneInfo.ConvertTimeToUtc(date1, tz));     
   }
}
// The example displays the following output on Windows XP systems:
//       3/21/2006 9:00:00 AM
//       3/21/2006 9:00:00 AM
//       3/21/2006 10:00:00 AM


The following example demonstrates the ToUniversalTime method.


			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); 


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

*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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