Gantt Chart Holidays

How do you enter Holidays from code without using the Holiday Editor? What is the structure to insert a holiday? I only want single days without time.

Holidays is a collection.

var
  h: TTMSFNCGanttHoliday;
begin
  h := TMSFNCGanttChart1.Project.WorkTime.Holidays.Add;
  h.StartDate := Now;
  h.EndDate := Now;
end;

There is also a helper function to do this in one line:
GanttChart.Project.WorkTime.Holidays.AddHoliday(StartDate: TDateTime, EndDate: TDateTime, AUseTime: Boolean = False);