System.Globalization.GregorianCalendarHelper.AddMonths C# (CSharp) Method

        public DateTime AddMonths(DateTime time, int months) 
        {
            CheckTicksRange(time.Ticks);
            if (months < -120000 || months > 120000) {
                throw new ArgumentOutOfRangeException(
                            "months", 
                            String.Format(
                                CultureInfo.CurrentCulture,
                                Environment.GetResourceString("ArgumentOutOfRange_Range"), 
                                -120000, 
                                120000));
            }
            int y = GetDatePart(time.Ticks, DatePartYear);
            int m = GetDatePart(time.Ticks, DatePartMonth);
            int d = GetDatePart(time.Ticks, DatePartDay);
            int i = m - 1 + months;
            if (i >= 0) 
            {
                m = i % 12 + 1;
                y = y + i / 12;
            }
            else 
            {
                m = 12 + (i + 1) % 12;
                y = y + (i - 11) / 12;
            }
            int[] daysArray = (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)) ? DaysToMonth366: DaysToMonth365;
            int days = (daysArray[m] - daysArray[m - 1]); 
            
            if (d > days) 
            {
                d = days;
            }
            long ticks = DateToTicks(y, m, d) + (time.Ticks % TicksPerDay);
            Calendar.CheckAddResult(ticks, m_Cal.MinSupportedDateTime, m_Cal.MaxSupportedDateTime);
            return (new DateTime(ticks));
        }
            

 public override DateTime AddMonths(DateTime time, int months)
 {
     return(helper.AddMonths(time, months));
 }