//1 

Console.WriteLine("Введите год рождения: ");
int year1 = int.Parse(Console.ReadLine());

for (int year = 1900; year < 2000; year++)
{
    for (int month = 1; month <= 12; month++)
    {
        for (int day = 1; day <= DateTime.DaysInMonth(year, month); day++)
        {
            DateTime date = new DateTime(year, month, day);
            int age = year1 - year;
            int sum1 = CalculateSumOfSquares(year) - (day * day);

            if (sum1 == age)
            {
                Console.WriteLine("Дата рождения по свойству Васи: " + date.ToShortDateString());
            }
        }
    }
}

static int CalculateSumOfSquares(int year)
{
    int sum = 0;
    foreach (char c in year.ToString())
    {
        sum += int.Parse(c.ToString()) * int.Parse(c.ToString());
    }
    return sum;
}