using System;

​

public class Program

{

    public static void Main()

    {

        DateTime dt = new DateTime(2015, 10, 15);

        //dt = DateTime.Now;

        double myOa = dt.ToOADate();

        Console.WriteLine("To OA: " + myOa.ToString());

        double myDbl = 42660.171277338;

        Console.WriteLine("From OA: "+DateTime.FromOADate(myDbl).ToString("yyyy-MM-dd HH:mm:ss"));

        Console.WriteLine("From 1 OA: "+DateTime.FromOADate(1).ToString("yyyy-MM-dd HH:mm:ss"));

    }

​

}