using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        CultureInfo provider = CultureInfo.InvariantCulture;

        // Save today's date.

        var today = DateTime.Today;

        string format = "yyyyMMdd";

        // Date of birth

        var dateOfBirth = new DateTime(1998, 01, 09);

​

        var a = (today.Year * 100 + today.Month) * 100 + today.Day;

        var b = (dateOfBirth.Year * 100 + dateOfBirth.Month) * 100 + dateOfBirth.Day;

​

        Console.WriteLine(a);       

        Console.WriteLine(b);

        Console.WriteLine( (a - b) / 10000);

        Console.WriteLine(DateTime.ParseExact(a.ToString(), format, provider));

}

}