To calculate total number of years

    public static class ExtensionMethods
    {
        public static IEnumerable<int> GetYearsUntilNow(this DateTime startDate)
        {
            for (int year = startDate.Year; year <= DateTime.Now.Year; ++year)
            {
                yield return year;
            }
        }
    }
</int>

var startDate = new DateTime(2009, 1, 8);
var years = startDate.GetYearsUntilNow();