Double - FromOADate

Returns a equivalent to the specified OLE Automation Date.

Try it

public static void Main()
{
    var arr = new double[]
    {
        39456,
        39482,
        39484,
        39493,
        39496,
        39497,
        39501,
        39506,
        39510,
        39513,
        39515,
        39521,
        36526,
        36557,
        39270 
    };

    foreach (double val in arr)
    {
        // C# Extension Method: Double - FromOADate
        DateTime oaDate = val.FromOADate();

        // Write to console.
        Console.WriteLine("{0} = {1}", val, oaDate.ToShortDateString());
    }
}

View Source 
using System;

public static partial class Extensions
{
    /// <summary>
    ///     Returns a  equivalent to the specified OLE Automation Date.
    /// </summary>
    /// <param name="d">An OLE Automation Date value.</param>
    /// <returns>An object that represents the same date and time as .</returns>
    public static DateTime FromOADate(this Double d)
    {
        return DateTime.FromOADate(d);
    }
}