System.Globalization.JulianCalendar.GetDatePart C# (CSharp) Méthode

        internal int GetDatePart(long ticks, int part)
        {
            // Gregorian 1/1/0001 is Julian 1/3/0001. Remember DateTime(0) is refered to Gregorian 1/1/0001.
            // The following line convert Gregorian ticks to Julian ticks.
            long julianTicks = ticks + TicksPerDay * 2;
            // n = number of days since 1/1/0001
            int n = (int)(julianTicks / TicksPerDay);
            // y4 = number of whole 4-year periods within 100-year period
            int y4 = n / JulianDaysPer4Years;
            // n = day number within 4-year period
            n -= y4 * JulianDaysPer4Years;
            // y1 = number of whole years within 4-year period
            int y1 = n / JulianDaysPerYear;
            // Last year has an extra day, so decrement result if 4
            if (y1 == 4) y1 = 3;
            // If year was requested, compute and return it
            if (part == DatePartYear)
            {
                return (y4 * 4 + y1 + 1);
            }
            // n = day number within year
            n -= y1 * JulianDaysPerYear;
            // If day-of-year was requested, return it
            if (part == DatePartDayOfYear)
            {
                return (n + 1);
            }
            // Leap year calculation looks different from IsLeapYear since y1, y4,
            // and y100 are relative to year 1, not year 0
            bool leapYear = (y1 == 3);
            int[] days = leapYear? DaysToMonth366: DaysToMonth365;
            // All months have less than 32 days, so n >> 5 is a good conservative
            // estimate for the month
            int m = n >> 5 + 1;
            // m = 1-based month number
            while (n >= days[m]) m++;
            // If month was requested, return it
            if (part == DatePartMonth) return (m);
            // Return 1-based day-of-month
            return (n - days[m - 1] + 1);
        }

        /// <summary>Returns a <see cref="T:System.DateTime" /> that is the specified number of months away from the specified <see cref="T:System.DateTime" />.</summary>
        /// <param name="time">The <see cref="T:System.DateTime" /> to which to add months. </param>
        /// <param name="months">The number of months to add. </param>
        /// <returns>The <see cref="T:System.DateTime" /> that results from adding the specified number of months to the specified <see cref="T:System.DateTime" />.</returns>
        /// <exception cref="T:System.ArgumentException">The resulting <see cref="T:System.DateTime" /> is outside the supported range. </exception>
        /// <exception cref="T:System.ArgumentOutOfRangeException">
        ///         <paramref name="months" /> is less than -120000.-or-
        ///         <paramref name="months" /> is greater than 120000. </exception>
        // Token: 0x06002F49 RID: 12105 RVA: 0x000B53F8 File Offset: 0x000B35F8
        public override DateTime AddMonths(DateTime time, int months)
        {
            if (months < -120000 || months > 120000)
            {
                throw new ArgumentOutOfRangeException("months", string.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("ArgumentOutOfRange_Range"), -120000, 120000));
            }
            int num  = JulianCalendar.GetDatePart(time.Ticks, 0);
            int num2 = JulianCalendar.GetDatePart(time.Ticks, 2);
            int num3 = JulianCalendar.GetDatePart(time.Ticks, 3);
            int num4 = num2 - 1 + months;

            if (num4 >= 0)
            {
                num2 = num4 % 12 + 1;
                num += num4 / 12;
            }
            else
            {
                num2 = 12 + (num4 + 1) % 12;
                num += (num4 - 11) / 12;
            }
            int[] array = (num % 4 == 0 && (num % 100 != 0 || num % 400 == 0)) ? JulianCalendar.DaysToMonth366 : JulianCalendar.DaysToMonth365;
            int   num5  = array[num2] - array[num2 - 1];

            if (num3 > num5)
            {
                num3 = num5;
            }
            long ticks = JulianCalendar.DateToTicks(num, num2, num3) + time.Ticks % 864000000000L;

            Calendar.CheckAddResult(ticks, this.MinSupportedDateTime, this.MaxSupportedDateTime);
            return(new DateTime(ticks));
        }