Polish Statutory Holidays

Business day calculations for offline invoice deadlines exclude weekends and Polish statutory holidays, as required by Polish law (Ordynacja podatkowa, art. 12 §5).

Holiday List

Source: Ustawa z dnia 18 stycznia 1951 r. o dniach wolnych od pracy (Dz.U. z 2025 r., poz. 296).

Fixed Holidays (10)

Date	Name	Notes
1 January	Nowy Rok	New Year's Day
6 January	Trzech Króli	Epiphany
1 May	Święto Państwowe	Labour Day
3 May	Święto Narodowe Trzeciego Maja	Constitution Day
15 August	Wniebowzięcie NMP	Assumption of Mary
1 November	Wszystkich Świętych	All Saints' Day
11 November	Narodowe Święto Niepodległości	Independence Day
24 December	Wigilia Bożego Narodzenia	Christmas Eve (since 2025)
25 December	Boże Narodzenie (1st day)	Christmas Day
26 December	Boże Narodzenie (2nd day)	St. Stephen's Day

Note: Christmas Eve (24 December) was added by the amendment of 6 December 2024 (Dz.U. 2024, poz. 1965), effective from 1 February 2025. For years before 2025, this date is not treated as a holiday.

Moveable Holidays (4, Easter-based)

Holiday	Calculation	Example (2026)
Wielkanoc (Easter Sunday)	Computus algorithm	5 April
Poniedziałek Wielkanocny (Easter Monday)	Easter + 1 day	6 April
Zielone Świątki (Pentecost)	Easter + 49 days	24 May
Boże Ciało (Corpus Christi)	Easter + 60 days	4 June

Pentecost always falls on a Sunday, so it does not affect business day calculations. It is included for legal completeness.

Total Count

• 14 holidays per year (2025 onwards)
• 13 holidays per year (2024 and earlier, before Wigilia amendment)

Implementation

The holiday logic is in src/offline/holidays.ts:

• computeEasterSunday(year) — computes Easter Sunday using the Anonymous Gregorian algorithm (Meeus/Jones/Butcher). Pure math, no external dependencies.
• getPolishHolidays(year) — returns a Set<string> of ISO date strings (YYYY-MM-DD) for all statutory holidays in the given year. Results are cached per year.
• isPolishHoliday(date) — checks if a UTC Date falls on a Polish statutory holiday.

These functions are used internally by nextBusinessDay() and addBusinessDays() in src/offline/deadline.ts. The integration is transparent — all deadline functions (calculateOfflineDeadline, extendDeadlineForMaintenance) automatically skip holidays without any API changes.

Usage

import {
  computeEasterSunday,
  getPolishHolidays,
  isPolishHoliday,
  nextBusinessDay,
} from 'ksef-client-ts';

// Easter Sunday for 2026
computeEasterSunday(2026); // → 2026-04-05

// All 14 holidays for 2026
const holidays = getPolishHolidays(2026);
// Set { '2026-01-01', '2026-01-06', '2026-04-05', ... }

// Check a specific date
isPolishHoliday(new Date('2026-12-25')); // → true (Christmas)
isPolishHoliday(new Date('2026-12-27')); // → false

// nextBusinessDay skips holidays automatically
nextBusinessDay(new Date('2026-12-23')); // Wed → Mon Dec 28
// (skips: Thu Dec 24 Wigilia, Fri Dec 25 Christmas, Sat-Sun weekend)

Holiday Clusters

Some holiday combinations create extended non-working periods. Examples for 2026:

Period	Non-working days	Next business day
Christmas 2026	Dec 24 (Thu, Wigilia) + Dec 25 (Fri) + Dec 26-27 (Sat-Sun)	Mon Dec 28
Easter 2026	Apr 5 (Sun, Easter) + Apr 6 (Mon, Easter Monday)	Tue Apr 7
May holidays 2026	May 1 (Fri) + May 2 (Sat) + May 3 (Sun, Constitution Day)	Mon May 4

These clusters are handled automatically — nextBusinessDay() and addBusinessDays() keep advancing until a working day is found.