System.Globalization.Calendar.AddYears C# (CSharp) Method

        public abstract DateTime AddYears(DateTime time, int years);

        internal void UpdateDecadeMode()
        {
            DateTime selectedYear;

            if (Owner != null)
            {
                selectedYear = Owner.DisplayYear;
            }
            else
            {
                selectedYear = DateTime.Today;
            }

            DateTime decade    = GetDecadeForDecadeMode(selectedYear);
            DateTime decadeEnd = _calendar.AddYears(decade, 9);

            SetDecadeModeHeaderButton(decade);
            SetDecadeModePreviousButton(decade);
            SetDecadeModeNextButton(decadeEnd);

            if (_yearView != null)
            {
                SetYearButtons(decade, decadeEnd);
            }
        }