kiahk 0.1.4

Coptic calendar arithmetic — date conversion, Easter, and feast days. Identical results across 7 language ports.

kiahk (Dart)

Coptic calendar arithmetic — date conversion, Easter, and feast days. Dart port of kiahk. Identical results to all other ports against core/test-vectors.json.

Package: https://pub.dev/packages/kiahk

Install

dart pub add kiahk

Or from this repo for development:

cd dart
dart pub get

Quick start

import 'package:kiahk/kiahk.dart';

void main() {
  // Convert Gregorian → Coptic
  final g = GregorianDate(2025, 1, 11);
  final c = g.toCoptic();
  print('${c.year} ${c.month} ${c.day}'); // 1741 5 3

  // Convert Coptic → Gregorian
  final c2 = CopticDate(1742, 1, 1);
  final g2 = c2.toGregorian();
  print('${g2.year} ${g2.month} ${g2.day}'); // 2025 9 11

  // Coptic Easter for a Gregorian year
  final easter = CopticCalendar.easterDate(2025);
  print('${easter.year} ${easter.month} ${easter.day}'); // 2025 4 20

  // All major feasts for a Gregorian year, sorted by date
  for (final feast in CopticCalendar.yearFeasts(2025)) {
    final d = feast.gregorianDate;
    print('${d.year}-${d.month.toString().padLeft(2, '0')}-${d.day.toString().padLeft(2, '0')}  ${feast.name('en')}');
  }
}

Sample output:

1741 5 3
2025 9 11
2025 4 20
2025-01-07  Nativity of Christ
2025-01-19  Epiphany (Theophany)
2025-02-10  Nineveh Fast
2025-02-24  Great Lent (start)
2025-04-07  Annunciation
2025-04-13  Palm Sunday
2025-04-20  Easter Sunday
2025-05-29  Ascension
2025-06-08  Pentecost
2025-08-22  Assumption of Mary
2025-09-27  Feast of the Cross

Render a date in English and Arabic

The library exposes Coptic month names in en + ar via CopticCalendar.monthName(month, locale). The full 13-entry table is also re-exported as kCopticMonths for callers that prefer raw data.

import 'package:kiahk/kiahk.dart';

void main() {
  final g = GregorianDate(2025, 4, 20);
  final c = g.toCoptic();
  print('${c.day} ${CopticCalendar.monthName(c.month, 'en')} ${c.year} AM');
  print('${c.day} ${CopticCalendar.monthName(c.month, 'ar')} ${c.year} للشهداء');
}

Sample output:

12 Parmouti 1741 AM
12 برمودة 1741 للشهداء

API at a glance

Type / method	Purpose
GregorianDate(y, m, d)	Validating constructor; throws InvalidGregorianDateException on bad input
GregorianDate.toCoptic() → CopticDate	Convert (extension method)
GregorianDate.toDateTime() / GregorianDate.fromDateTime(dt)	Interop with DateTime
CopticDate(y, m, d)	Validating constructor; throws InvalidCopticDateException on bad input
CopticDate.toGregorian() → GregorianDate	Convert
Feast	id, type, category, names, gregorianDate, name(locale)
Feast.name('fr')	Throws UnsupportedLocaleException for unknown locale
CopticCalendar.easterDate(year) → GregorianDate	Coptic Easter
CopticCalendar.moveableFeast(feastId, year) → Feast	One moveable feast
CopticCalendar.yearFeasts(year) → List<Feast>	All feasts, sorted ascending
CopticCalendar.monthName(month, locale) → String	Coptic month name; throws InvalidCopticMonthException / UnsupportedLocaleException
kCopticMonths	13-entry List<CopticMonthRecord> (mirrors core/coptic_months.json)

Supported locales for Feast.name(...) and CopticCalendar.monthName(...): en, ar.

Run tests

cd dart
dart test

License

Licensed under the MIT License.

Maintained by Amir Magdy at WizardLabz.