ChronosBridge

Universal calendar conversion engine for JavaScript.

ChronosBridge focuses on mathematical calendar logic only:

• Gregorian
• Hebrew
• Islamic
• Persian (Jalali)
• Julian Day Number (JDN) bridge

Scope

This package does not include:

• country-specific holiday laws
• legal-day classification
• localization/business rules

Calendar Models (Important)

ChronosBridge currently uses deterministic algorithmic/tabular models. It does not use observational moon-sighting datasets.

• Islamic: arithmetic/tabular model (30-year leap cycle), not moon-sighting based.
• Hebrew: fixed calculated rabbinic calendar (Metonic cycle + rule-based month lengths).
• Persian (Jalali): arithmetic conversion model, not observatory/equinox-per-location calculation.

This is expected to produce differences vs. regional religious authorities or observational calendars in some cases.

Project Layout

chronos-bridge/
├── src/
│   ├── calendars/
│   ├── core/
│   └── index.js
├── tests/
├── index.js
└── package.json

Usage

import { convert, toJdn, fromJdn } from "chronos-bridge";

const jdn = toJdn("gregorian", { year: 2026, month: 5, day: 12 });
const islamic = fromJdn("islamic", jdn);
const hebrew = convert("gregorian", "hebrew", { year: 2026, month: 5, day: 12 });

console.log({ jdn, islamic, hebrew });

Supported Conversions

All conversions are routed through JDN:

Calendar A -> JDN -> Calendar B

Currently supported in the public bridge:

• Gregorian <-> JDN
• Islamic <-> JDN
• Hebrew <-> JDN
• Persian <-> JDN

This means cross-conversions like these are supported via convert(...):

• Gregorian <-> Islamic
• Gregorian <-> Hebrew
• Gregorian <-> Persian
• Islamic <-> Hebrew
• Islamic <-> Persian
• Hebrew <-> Persian

Development Notes

• Keep calculations deterministic and UTC-based.
• Add tests for every algorithm change.
• Treat this repository as the shared core for higher-level domain packages.

License

MIT