Convert a two digit year to a four digit year

Question

This is a question of best practices. I have a utility that takes in a two digit year as a string and I need to convert it to a four digit year as a string. right now I do <

Answer 1

This Method can convert the credit card last two year digits to four year

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private static int ToFourDigitYear(int year)
{
    string stringYear = year.ToString("00");
    if (stringYear.Length == 2)
    {
        int currentYear = DateTime.Now.Year;
        string firstTwoDigitsOfCurrentYear = currentYear.ToString().Substring(0, 2);
        year = Convert.ToInt32(firstTwoDigitsOfCurrentYear + stringYear);
        if (year < currentYear)
            year = year + 100;
    }
    return year;
}