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DateTime.FromFileTime(Int64) Method

Definition

Converts the specified Windows file time to an equivalent local time.

public:
 static DateTime FromFileTime(long fileTime);
public static DateTime FromFileTime (long fileTime);
static member FromFileTime : int64 -> DateTime
Public Shared Function FromFileTime (fileTime As Long) As DateTime

Parameters

fileTime
Int64

A Windows file time expressed in ticks.

Returns

An object that represents the local time equivalent of the date and time represented by the fileTime parameter.

Exceptions

fileTime is less than 0 or represents a time greater than DateTime.MaxValue.

Examples

The following example demonstrates the FromFileTime method.

System::TimeSpan FileAge( long fileCreationTime )
{
   System::DateTime now = System::DateTime::Now;
   try
   {
      System::DateTime fCreationTime =
         System::DateTime::FromFileTime( fileCreationTime );
      System::TimeSpan fileAge = now.Subtract( fCreationTime );
      return fileAge;
   }
   catch ( ArgumentOutOfRangeException^ ) 
   {
      // fileCreationTime is not valid, so re-throw the exception.
      throw;
   }
}
open System

let fileAge fileCreationTime =
    let now = DateTime.Now
    try
        let fCreationTime =
            DateTime.FromFileTime fileCreationTime
        now.Subtract fCreationTime
    with :? ArgumentOutOfRangeException ->
        // fileCreationTime is not valid, so re-raise the exception.
        reraise ()
public System.TimeSpan FileAge(long fileCreationTime) {

    System.DateTime now = System.DateTime.Now;
    try {
        System.DateTime fCreationTime =
            System.DateTime.FromFileTime(fileCreationTime);
        System.TimeSpan fileAge = now.Subtract(fCreationTime);
        return fileAge;				
    }
    catch (ArgumentOutOfRangeException) {
        // fileCreationTime is not valid, so re-throw the exception.
        throw;
    }
}
Public Function FileAge(ByVal fileCreationTime As Long) As System.TimeSpan
   Dim now As System.DateTime
   now = System.DateTime.Now

   Try
      Dim fCreationTime As System.DateTime
      Dim fAge As System.TimeSpan
      fCreationTime = System.DateTime.FromFileTime(fileCreationTime)
      fAge = now.Subtract(fCreationTime)
      Return fAge
   Catch exp As ArgumentOutOfRangeException
      ' fileCreationTime is not valid, so re-throw the exception.
      Throw
   End Try
End Function

Remarks

A Windows file time is a 64-bit value that represents the number of 100-nanosecond intervals that have elapsed since 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC). Windows uses a file time to record when an application creates, accesses, or writes to a file.

The fileTime parameter specifies a file time expressed in 100-nanosecond ticks.

Starting with the .NET Framework version 2.0, the return value is a DateTime whose Kind property is DateTimeKind.Local.

Notes to Callers

Ordinarily, the FromFileTime(Int64) method restores a DateTime value that was saved by the ToFileTime() method. However, the two values may differ under the following conditions:

  • If the serialization and deserialization of the DateTime value occur in different time zones. For example, if a DateTime value with a time of 12:30 P.M. in the U.S. Eastern Time zone is serialized, and then deserialized in the U.S. Pacific Time zone, the original value of 12:30 P.M. is adjusted to 9:30 A.M. to reflect the difference between the two time zones.

  • If the DateTime value that is serialized represents an invalid time in the local time zone. In this case, the ToFileTime() method adjusts the restored DateTime value so that it represents a valid time in the local time zone.

    For 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. This hour interval is an invalid time, that is, a time interval that does not exist in this time zone. The following example shows that when a time that falls within this range is converted to a long integer value by the ToFileTime() method and is then restored by the FromFileTime(Int64) method, the original value is adjusted to become a valid time. 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.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          DateTime date1 = new DateTime(2010, 3, 14, 2, 30, 00);
          Console.WriteLine("Invalid Time: {0}",
                            TimeZoneInfo.Local.IsInvalidTime(date1));
          long ft = date1.ToFileTime();
          DateTime date2 = DateTime.FromFileTime(ft);
          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, 00)
    printfn $"Invalid Time: {TimeZoneInfo.Local.IsInvalidTime date1}"
    
    let ft = date1.ToFileTime()
    let date2 = DateTime.FromFileTime ft
    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 DateTime(2010, 3, 14, 2, 30, 00)
          Console.WriteLine("Invalid Time: {0}", TimeZoneInfo.Local.IsInvalidTime(date1))
          Dim ft As Long = date1.ToFileTime()
          Dim date2 As DateTime = DateTime.FromFileTime(ft)
          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
    

Applies to

See also