DateTime::FromFileTime Method (Int64)


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

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

static DateTime FromFileTime(
	long long fileTime


Type: System::Int64

A Windows file time expressed in ticks.

Return Value

Type: System::DateTime

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

Exception Condition

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

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 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 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 TimeZoneInfo::IsInvalidTime method, as the example illustrates.

    No code example is currently available or this language may not be supported.

The following example demonstrates the FromFileTime method.

System::TimeSpan FileAge( long fileCreationTime )
   System::DateTime now = System::DateTime::Now;
      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.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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