AgeAfter10Years

using System;
using System.Globalization; // needed for the DateTime.TryParseExact

class AgeAfterTenYears
{

    static void Main()
    {
        bool notYetBorn = true;
        bool invalidDateFormat = true;

        while (invalidDateFormat)
        {
            while (notYetBorn)
            {

                Console.WriteLine("Please enter a valid birthday (yyyy.mm.dd):");
                string birthDay = Console.ReadLine();
                
                DateTime dateTime;
                string format = "yyyy.M.d";

                if (DateTime.TryParseExact(birthDay, format, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime)) 
                    //cheking if the format of the input is correct.
                {
                    invalidDateFormat = false; //if format is corect this will end the loop

                    DateTime today = DateTime.Now;
                    int age = today.Year - dateTime.Year; //calculating the age
                    if (dateTime > today.AddYears(-age)) age--; // adjusts the age according to what date is today

                    if (dateTime.Date <= today.Date) //checkes if the input is a future date
                    {
                        Console.WriteLine("You are {0} years old.", age);
                        Console.WriteLine("After 10 years you will be {0} years old", age + 10);
                        notYetBorn = false; // this will end the loop
                    }
                    else
                    {
                        Console.WriteLine("You are NOT yet born."); // if you have added a future date this will be printed
                    }
                }

                else
                {
                    Console.WriteLine("Invalid date format."); // if you have added an invalid date it will print this warning.
                }
            }
        }
    }
}