DateTime.ToFileTime() Method in C#

The DateTime.ToFileTime() method in C# converts the value of the current DateTime object to a Windows file time. Windows file time represents the number of 100-nanosecond intervals that have elapsed since 12:00 midnight, January 1, 1601 A.D. (UTC).

This method is particularly useful when working with file system operations, as Windows uses this format internally for file timestamps.

Syntax

Following is the syntax −

public long ToFileTime();

Return Value

The method returns a long value representing the current DateTime object as a Windows file time.

How It Works

The method performs the following conversion process −

Using ToFileTime() with Current DateTime

Example

using System;

public class Demo {
   public static void Main() {
      DateTime d = DateTime.Now;
      Console.WriteLine("Date = {0}", d);
      long res = d.ToFileTime();
      Console.WriteLine("Windows file time = {0}", res);
      
      // Convert back to verify
      DateTime converted = DateTime.FromFileTime(res);
      Console.WriteLine("Converted back = {0}", converted);
   }
}

The output of the above code is −

Date = 10/16/2019 8:17:26 AM
Windows file time = 132156874462559390
Converted back = 10/16/2019 8:17:26 AM

Using ToFileTime() with Specific DateTime

Example

using System;

public class Demo {
   public static void Main() {
      DateTime d = new DateTime(2019, 05, 10, 6, 10, 25);
      Console.WriteLine("Date = {0}", d);
      long res = d.ToFileTime();
      Console.WriteLine("Windows file time = {0}", res);
      
      // Calculate difference from epoch
      DateTime epoch = new DateTime(1601, 1, 1);
      TimeSpan difference = d.ToUniversalTime() - epoch;
      Console.WriteLine("Total 100-nanosecond ticks = {0}", difference.Ticks);
   }
}

The output of the above code is −

Date = 5/10/2019 6:10:25 AM
Windows file time = 132019422250000000
Total 100-nanosecond ticks = 132019422250000000

Common Use Cases

• File System Operations − Working with file creation, modification, and access times.

• Windows API Integration − Interfacing with Windows APIs that expect file time format.

• Database Storage − Storing timestamps in a compact, standardized format.

• Network Protocols − Some protocols use Windows file time for timestamp representation.

Conclusion

The DateTime.ToFileTime() method converts a DateTime object to Windows file time format, represented as 100-nanosecond intervals since January 1, 1601 UTC. This method is essential for file system operations and Windows API integration where precise timestamp representation is required.