Program

using System;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            DateTime dt1;
            
            Console.WriteLine("Time before set last write time in UTC:");
           
            dt1 = File. SetLastWriteTimeUtc("ABC.TXT");
            Console.WriteLine("\tLast write Time of file(ABC.TXT) : " + dt1);

            
            File. SetLastWriteTimeUtc("ABC.TXT", DateTime.Now);
           
            Console.WriteLine("Time After set last write time in UTC:");
           
            dt1 = File. SetLastWriteTime("ABC.TXT");
            Console.WriteLine("\tLast write Time of file(ABC.TXT) : " + dt1);

           
        }
    }
}

Output

Time before set last write time in UTC:
        Last write  Time of file(ABC.TXT) : 10/31/2017 4:25:36 PM
Time After set last write  time in UTC :
        Last write  Time of file(ABC.TXT) : 10/31/2017 4:37:29 PM

Note: In above program, we need to remember, when we use "File" class, System.IO namespace must be included in the program.