Table of Contents

Work-time calendar

The work-time calendar turns durations into real dates. When a task is scheduled with a working-time policy, the project counts only working days and working hours and skips holidays — so "3 working days" starting Friday lands the finish on the following Wednesday rather than Monday. The calendar lives on Project.WorkTime and is shared by every task. This chapter covers configuring working days, working hours, and holidays, and how each task's WorkTimePolicy decides which of those rules apply.

Working days, hours, and holidays

WorkTime exposes three pieces: WorkingDays (a set of gdMonday…gdSunday), WorkingHours (a collection of daily intervals via AddTimeSpan), and Holidays (date ranges via AddHoliday). Configure them inside a BeginUpdate/EndUpdate pair so the project recalculates once:

procedure TForm1.ConfigureCalendar;
begin
  GanttProject1.BeginUpdate;
  try
    // Working days: Monday through Friday.
    GanttProject1.WorkTime.WorkingDays :=
      [gdMonday, gdTuesday, gdWednesday, gdThursday, gdFriday];

    // Working hours: 09:00–12:00 and 13:00–17:00.
    GanttProject1.WorkTime.WorkingHours.Clear;
    GanttProject1.WorkTime.WorkingHours.AddTimeSpan(EncodeTime(9, 0, 0, 0),
      EncodeTime(12, 0, 0, 0));
    GanttProject1.WorkTime.WorkingHours.AddTimeSpan(EncodeTime(13, 0, 0, 0),
      EncodeTime(17, 0, 0, 0));

    // A company holiday excluded from scheduling.
    GanttProject1.WorkTime.Holidays.Clear;
    GanttProject1.WorkTime.Holidays.AddHoliday(EncodeDate(2026, 12, 25));
  finally
    GanttProject1.EndUpdate;
  end;

  // Tasks added with whWorkTimeAndDays now skip weekends, off-hours, and holidays.
  GanttProject1.AddTask('Kickoff', 'Project start',
    EncodeDate(2026, 12, 24), 3, gdtWorkDays, whWorkTimeAndDays);
end;
A chart where task bars skip a weekend and a holiday A chart where task bars skip a weekend and a holiday

Work-time policies

Each task's WorkTimePolicy selects which calendar rules apply when its schedule is calculated:

Value Schedules using
whWorkTimeAndDays Working hours and working days (skips off-hours, weekends, holidays)
whWorkTimeOnly Working hours on any day
whWorkDaysOnly Whole working days, ignoring working-hour ranges
whAllTime Continuous calendar time, no restrictions

Pass the policy as an argument to AddTask/AddSubTask, or set Task.WorkTimePolicy afterward. Use whWorkTimeAndDays for office work, whAllTime for machine or elapsed-time tasks.

Querying the calendar

WorkTime also answers calendar questions directly: IsWorkDay, IsWorkTime, IsHoliday, and WorkDayStart / WorkDayEnd. These are useful when you place tasks at the start of a working day, as the demos do with WorkTime.WorkDayStart.

Putting it together — calendar, hierarchy, and a dependency

A realistic project combines all three areas: a weekday calendar, a task hierarchy, and a dependency, then renders through a chart. This is the setup the screenshots above are captured from:

procedure TForm1.BuildScheduledProject;
var
  Design, Build, Sub: TTMSFNCGanttTask;
begin
  GanttChart1.Project := GanttProject1;

  GanttProject1.BeginUpdate;
  try
    GanttProject1.ClearTasks;

    // 1. Calendar: weekdays only, 9–17.
    GanttProject1.WorkTime.WorkingDays :=
      [gdMonday, gdTuesday, gdWednesday, gdThursday, gdFriday];
    GanttProject1.WorkTime.WorkingHours.Clear;
    GanttProject1.WorkTime.WorkingHours.AddTimeSpan(EncodeTime(9, 0, 0, 0),
      EncodeTime(17, 0, 0, 0));

    // 2. Hierarchy: a phase with two subtasks.
    Design := GanttProject1.AddTask('Design', 'Visual design',
      Now, 3, gdtWorkDays, whWorkTimeAndDays, 100);
    Sub := Design.AddSubTask('Wireframes', '', Now, 1, gdtWorkDays,
      whWorkTimeAndDays, 100);
    Sub := Design.AddSubTask('Mockups', '', 0, 2, gdtWorkDays,
      whWorkTimeAndDays, 50);

    // 3. Dependency: Build follows Design.
    Build := GanttProject1.AddTask('Build', 'Implementation',
      0, 5, gdtWorkDays);
    Build.TaskDependencies.AddDependency(Design, gtdFinishToStart);
  finally
    GanttProject1.EndUpdate;
  end;
end;

Pitfalls

  • A duration in gdtWorkDays is only meaningful when a working-time policy is active. With whAllTime, "3 work days" is treated as continuous calendar time.
  • Clear WorkingHours before adding spans if you are replacing the defaults — AddTimeSpan appends.
  • Holidays added with UseTime := False cover the whole day; set UseTime to restrict a holiday to a time range.

See also