Kiahk 0.1.5

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Kiahk (C#)

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

Package: https://www.nuget.org/packages/Kiahk/

Install

dotnet add package Kiahk

Or from this repo for development:

cd csharp
dotnet build

Quick start

using Kiahk;

// Convert Gregorian → Coptic
var g = new GregorianDate(2025, 1, 11);
var c = g.ToCoptic();
Console.WriteLine($"{c.Year} {c.Month} {c.Day}"); // 1741 5 3

// Convert Coptic → Gregorian
var c2 = new CopticDate(1742, 1, 1);
var g2 = c2.ToGregorian();
Console.WriteLine($"{g2.Year} {g2.Month} {g2.Day}"); // 2025 9 11

// Coptic Easter for a Gregorian year
var easter = CopticCalendar.EasterDate(2025);
Console.WriteLine($"{easter.Year} {easter.Month} {easter.Day}"); // 2025 4 20

// All major feasts for a Gregorian year, sorted by date
foreach (var feast in CopticCalendar.YearFeasts(2025))
{
    var d = feast.GregorianDate;
    Console.WriteLine($"{d.Year}-{d.Month:D2}-{d.Day:D2}  {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 CopticMonthsData.Months for callers that prefer raw data.

using Kiahk;

var g = new GregorianDate(2025, 4, 20);
var c = g.ToCoptic();
Console.WriteLine($"{c.Day} {CopticCalendar.MonthName(c.Month, "en")} {c.Year} AM");
Console.WriteLine($"{c.Day} {CopticCalendar.MonthName(c.Month, "ar")} {c.Year} للشهداء");

Sample output:

12 Parmouti 1741 AM
12 برمودة 1741 للشهداء

API at a glance

Supported locales for Feast.Name(...) and CopticCalendar.MonthName(...): en, ar.

Algorithm primitives are exposed via Kiahk.Algorithms (static class): GregorianToJdn, JdnToGregorian, CopticToJdn, JdnToCoptic, GregorianToCoptic, CopticToGregorian, ComputeEaster, AddDays — all return (int Year, int Month, int Day) named tuples.

Run tests

cd csharp
dotnet test

License

Licensed under the MIT License.

Maintained by Amir Magdy at WizardLabz.