protected virtual TimeSpan DoCalcDuration(DateTime start, DateTime end, TimeZoneInfo timeZone = null) { if (start.Equals(end)) { return(TimeSpan.Zero); } // test range TimeRange testRange = new TimeRange(start, end); // search range DateTime searchStart = new Day(testRange.Start).Start; DateTime serachEnd = new Day(testRange.End).GetNextDay().Start; TimeRange searchPeriod = new TimeRange(searchStart, serachEnd); // exclude periods _filter.ExcludePeriods.Clear(); _filter.ExcludePeriods.AddAll(_excludePeriods); // collect hours TimeCalendar calendar = new TimeCalendar(new TimeCalendarConfig { EndOffset = TimeSpan.Zero }); CalendarPeriodCollector collector = new CalendarPeriodCollector(_filter, searchPeriod, SeekDirection.Forward, calendar); collector.CollectHours(); TimeSpan duration = TimeSpan.Zero; collector.Periods.AddAll(_includePeriods); foreach (ICalendarTimeRange period in collector.Periods) { // get the intersection of the test-range and the day hours ITimePeriod intersection = testRange.GetIntersection(period); if (intersection == null) { continue; } duration = duration.Add(DurationProvider.GetDuration(intersection.Start, intersection.End)); } return(start < end ? duration : duration.Negate()); }