kiahk (JavaScript / TypeScript)

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

Works in Node.js and the browser — no Node-only APIs at runtime.

Package: https://www.npmjs.com/package/kiahk Live demo: https://raw.githack.com/amir-magdy-of-wizardlabz/kiahk/master/demo/index.html

Install

npm install kiahk

Or from this repo for development:

cd js
npm install
npm run build
npm test

Quick start

import { CopticDate, GregorianDate, CopticCalendar } from 'kiahk'

// Convert Gregorian → Coptic
const g = new GregorianDate(2025, 1, 11)
const c = g.toCoptic()
console.log(c.year, c.month, c.day) // 1741 5 3

// Convert Coptic → Gregorian
const c2 = new CopticDate(1742, 1, 1)
const g2 = c2.toGregorian()
console.log(g2.year, g2.month, g2.day) // 2025 9 11

// Coptic Easter for a Gregorian year
const easter = CopticCalendar.easterDate(2025)
console.log(easter.year, easter.month, easter.day) // 2025 4 20

// All major feasts for a Gregorian year, sorted by date
for (const feast of CopticCalendar.yearFeasts(2025)) {
  const d = feast.gregorianDate
  const pad = n => String(n).padStart(2, '0')
  console.log(`${d.year}-${pad(d.month)}-${pad(d.day)}  ${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 COPTIC_MONTHS for callers that prefer raw data.

import { GregorianDate, CopticCalendar } from 'kiahk'

const g = new GregorianDate(2025, 4, 20)
const c = g.toCoptic()
console.log(`${c.day} ${CopticCalendar.monthName(c.month, 'en')} ${c.year} AM`)
console.log(`${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 | | --- | --- | | new GregorianDate(y, m, d) | Validating constructor; throws InvalidGregorianDateException on bad input | | GregorianDate#toCoptic() → CopticDate | Convert | | GregorianDate#toNativeDate() / GregorianDate.fromNativeDate(d) | Interop with JS Date | | new CopticDate(y, m, d) | Validating constructor; throws InvalidCopticDateException on bad input | | CopticDate#toGregorian() → GregorianDate | Convert | | Feast | id, type, category, 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) → Feast[] | All feasts, sorted ascending | | CopticCalendar.monthName(month, locale) → string | Coptic month name; throws InvalidCopticMonthException / UnsupportedLocaleException | | COPTIC_MONTHS | 13-entry array (mirrors core/coptic_months.json) |

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

Run tests

cd js
npm test

License

Licensed under the MIT License.

Maintained by Amir Magdy at WizardLabz.