Business calendars

ChronoKit-FP uses Monday through Friday when you call a business-day helper without a calendar. Create a TBusinessCalendar when you also need holidays or a different working week.

var
  Calendar: TBusinessCalendar;
begin
  Calendar := TChronoKit.CreateBusinessCalendar([
    EncodeDate(2026, 1, 1),
    EncodeDate(2026, 12, 25)
  ]);
end;

For a Sunday-to-Thursday week, pass the working days explicitly:

Calendar := TChronoKit.CreateBusinessCalendar(
  [bwdSunday, bwdMonday, bwdTuesday, bwdWednesday, bwdThursday],
  [EncodeDate(2026, 1, 1)]
);

Pass the calendar as the final argument to IsBusinessDay, NextBusinessDay, PreviousBusinessDay, AddBusinessDays, or BusinessDaysBetween.

Deadline recipe#

This complete program calculates a five-business-day deadline while excluding a public holiday:

program BusinessDeadline;

{$mode objfpc}{$H+}{$J-}

uses
  SysUtils,
  ChronoKit;

var
  Calendar: TBusinessCalendar;
  Submitted, DueDate: TDateTime;
begin
  Calendar := TChronoKit.CreateBusinessCalendar([
    EncodeDate(2026, 8, 10)
  ]);
  Submitted := EncodeDate(2026, 8, 7);
  DueDate := TChronoKit.AddBusinessDays(Submitted, 5, Calendar);

  WriteLn(TChronoKit.FormatDateTime(DueDate, 'yyyy-mm-dd'));
end.

The result is 2026-08-17. The starting date is not counted.

Reporting-period recipe#

Count the working dates in a calendar month with the inclusive counting operation:

WorkingDaysInAugust := TChronoKit.BusinessDaysBetween(
  EncodeDate(2026, 8, 1),
  TChronoKit.EndOfMonth(EncodeDate(2026, 8, 1)),
  Calendar
);

Both qualifying endpoints are counted. Reverse the dates to receive the negative of the forward count. Time portions are accepted and ignored.

Date-range recipe#

Build an inclusive list by iterating over calendar dates and keeping only those accepted by the calendar:

CurrentDate := EncodeDate(2026, 8, 7);
EndDate := EncodeDate(2026, 8, 14);

while CurrentDate <= EndDate do
begin
  if TChronoKit.IsBusinessDay(CurrentDate, Calendar) then
    WriteLn(TChronoKit.FormatDateTime(CurrentDate, 'yyyy-mm-dd'));
  CurrentDate := TChronoKit.AddDays(CurrentDate, 1);
end;

This pattern makes both endpoints explicit. It is useful for report rows, booking availability, and working-date exports.

Boundary behavior#

• Holidays are compared by date; a time stored in a holiday value is ignored.
• Returned dates preserve the input time.
• NextBusinessDay and PreviousBusinessDay are strict and never return the

starting date.

• AddBusinessDays does not count the starting date. Zero returns the exact

input, including when it falls on a non-working day.

• BusinessDaysBetween counts qualifying start and end dates inclusively. A

same-day business date returns 1; a same-day non-business date returns 0. Reverse endpoint order reverses the result sign.

• Leap days, month ends, and year ends follow normal calendar arithmetic.
• An empty working week raises EBusinessCalendarError; select at least one

TBusinessWeekday.

• Duplicate holidays and holidays already outside the working week have no

additional effect.

The accepted API contract and alternatives are recorded in Business-calendar API design.