ToFileTime Method

DateTime.ToFileTime Method ()


Converts the value of the current DateTime object to a Windows file time.

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

public long ToFileTime()

Return Value

Type: System.Int64

The value of the current DateTime object expressed as a Windows file time.

Exception Condition

The resulting file time would represent a date and time before 12:00 midnight January 1, 1601 C.E. UTC.

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 ToFileTime method uses the Kind property to determine whether the current DateTime object is a local time, a UTC time, or an unspecified kind of time which is treated as a local time.

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.

    public void DisplayAttributes(XmlReader reader)
      if (reader.HasAttributes)
        Console.WriteLine("Attributes of <" + reader.Name + ">");
        for (int i = 0; i < reader.AttributeCount; i++)
          Console.Write(" {0}={1}", reader.Name, reader.Value);
        reader.MoveToElement(); //Moves the reader back to the element node.

The following example demonstrates the ToFileTime method.

static void Main(string[] args)
	System.Console.WriteLine("Enter the file path:");
	string filePath = System.Console.ReadLine();

	if (System.IO.File.Exists(filePath)) {
		System.DateTime fileCreationDateTime = 

		long fileCreationFileTime = fileCreationDateTime.ToFileTime();

		System.Console.WriteLine("{0} in file time is {1}.",
	else {
		System.Console.WriteLine("{0} is an invalid file", filePath);

Universal Windows Platform
Available since 4.5
.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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