ExtractInfoFromUserID

using System;

namespace ExtractInfoFromUserID
{
    class ExtractInfoFromUserID
    {
        static void Main()
        {
            Console.WriteLine("Enter your ID (ID must be a 10 digit number): ");
            string id = Console.ReadLine();
            //validate user id
            if (id.Length != 10)
            {
                Console.WriteLine("Invalid ID!");
            }
            else
            {
                Console.WriteLine("Valid ID");
            }
            //define user gender
            string gender = id.Substring(8, 1);
            int genderChecked = int.Parse(gender);
            if (genderChecked % 2 == 0)
            {
                Console.WriteLine("Gender: Male");
            }
            else
            {
                Console.WriteLine("Gender: Female");
            }
            //define user age
            string yearOfBirth = id.Substring(0, 2);
            int year = int.Parse(yearOfBirth);
            string monthChecked = id.Substring(2, 2);
            int monthResult = int.Parse(monthChecked);
            if (monthResult >= 21 && monthResult <= 32)
            {
                year += 1800;
            }
            else if (monthResult > +41 && monthResult < +52)
            {
                year += 2000;
            }
            else
            {
                year += 1900;
            }
            Console.WriteLine("Year of birth: " + year);
            string dayOfBirth = id.Substring(4, 2);
            string monthOfBirth = id.Substring(2, 2);
            //days left till next birthday
            int day = int.Parse(dayOfBirth);
            int month = int.Parse(monthOfBirth);
            int userAge = 0;
            userAge = DateTime.Now.Year - year;
            Console.WriteLine("User age: " + userAge);
            //write user birthday on the console
            if (year >= 2000)
            {
                month = month - 40;
            }
            if (year <= 1900)
            {
                month = month - 20;
            }
            Console.WriteLine("User birthday: {0}.{1}.{2}", dayOfBirth, month, year);
            DateTime futureDate = new DateTime(DateTime.Now.Year, month, day);
            Console.WriteLine("Next birthday: {0:dd/MM/yyyy}", futureDate);
            DateTime currentDate = new DateTime();
            currentDate = DateTime.Now;
            TimeSpan days = futureDate.Date - currentDate.Date;
            int daysLeft = (int)days.TotalDays;
            Console.WriteLine("Days left till next user birthday: {0}", daysLeft);
        }
    }
}