Fan.Sys.TimeZone.Rule.isWallTime C# (CSharp) Method

            public bool isWallTime()
            {
                return dstStart.atMode == 'w';
            }

        private DateTime(long ticks, TimeZone tz)
        {
            // check boundary conditions 1901 to 2099
            if (ticks < minTicks || ticks >= maxTicks)
            {
                throw ArgErr.make("Ticks out of range 1901 to 2099").val;
            }

            // save ticks, time zone
            this.m_ticks = ticks;
            this.m_tz    = tz;

            // compute the year
            int year = ticksToYear(ticks);

            // get the time zone rule for this year, and
            // offset the working ticks by UTC offset
            TimeZone.Rule rule = m_tz.rule(year);
            ticks += rule.offset * nsPerSec;

            // compute the day and month; we may need to execute this
            // code block up to three times:
            //   1st: using standard time
            //   2nd: using daylight offset (if in dst)
            //   3rd: using standard time (if dst pushed us back into std)
            int  month, day, dstOffset = 0;
            long rem;

            while (true)
            {
                // recompute year based on working ticks
                year = ticksToYear(ticks);
                rem  = ticks - yearTicks[year - 1900];
                if (rem < 0)
                {
                    rem += nsPerYear;
                }

                // compute day of the year
                int dayOfYear = (int)(rem / nsPerDay);
                rem %= nsPerDay;

                // use lookup tables map day of year to month and day
                if (isLeapYear(year))
                {
                    month = monForDayOfYearLeap[dayOfYear];
                    day   = dayForDayOfYearLeap[dayOfYear];
                }
                else
                {
                    month = monForDayOfYear[dayOfYear];
                    day   = dayForDayOfYear[dayOfYear];
                }

                // if dstOffset is set to max, then this is
                // the third time thru the loop: std->dst->std
                if (dstOffset == System.Int32.MaxValue)
                {
                    dstOffset = 0; break;
                }

                // if dstOffset is non-zero we have run this
                // loop twice to recompute the date for dst
                if (dstOffset != 0)
                {
                    // if our dst rule is wall time based, then we need to
                    // recompute to see if dst wall time pushed us back
                    // into dst - if so then run through the loop a third
                    // time to get us back to standard time
                    if (rule.isWallTime() && TimeZone.dstOffset(rule, year, month, day, (int)(rem / nsPerSec)) == 0)
                    {
                        ticks    -= dstOffset * nsPerSec;
                        dstOffset = System.Int32.MaxValue;
                        continue;
                    }
                    break;
                }

                // first time in loop; check for daylight saving time,
                // and if dst is in effect then re-run this loop with
                // modified working ticks
                dstOffset = TimeZone.dstOffset(rule, year, month, day, (int)(rem / nsPerSec));
                if (dstOffset == 0)
                {
                    break;
                }
                ticks += dstOffset * nsPerSec;
            }

            // compute time of day
            int hour = (int)(rem / nsPerHour);  rem %= nsPerHour;
            int min  = (int)(rem / nsPerMin);   rem %= nsPerMin;

            // compute weekday
            int weekday = (firstWeekday(year, month) + day - 1) % 7;

            // fields
            int fields = 0;

            fields       |= ((year - 1900) & 0xff) << 0;
            fields       |= (month & 0xf) << 8;
            fields       |= (day & 0x1f) << 12;
            fields       |= (hour & 0x1f) << 17;
            fields       |= (min & 0x3f) << 22;
            fields       |= (weekday & 0x7) << 28;
            fields       |= (dstOffset != 0 ? 1 : 0) << 31;
            this.m_fields = fields;
        }