hebrewcal 0.1.1

A pure-Python library for the Hebrew calendar: conversion, astronomy, holidays and religious times, computed entirely locally.

hebrewcal

A pure-Python library for the Hebrew calendar.

hebrewcal makes the Hebrew calendar usable programmatically and converts it bidirectionally against the Gregorian and Julian calendars. Every computation is performed locally — the library never issues network calls to any external service.

It is built for two audiences:

• Religious use — holidays (Israel and the Diaspora, including minority feasts and Shushan Purim), Shabbat candle lighting and Havdalah, zmanim, Torah readings, the Omer count, yahrzeit, and the sabbatical and jubilee cycle.
• Academic use — historical, medieval and ancient dates, Babylonian and biblical month names, proleptic calendars, the Julian/Gregorian reform, and the documented "missing years" of the Anno Mundi count.

Project status. Early development. The calendar core, conversion and date handling (Phase 1) are implemented. Astronomy, holidays and religious times follow on the roadmap.

Installation

pip install hebrewcal

hebrewcal requires Python 3.11+ and has no runtime dependencies (standard library only).

Quick start

from hebrewcal import GregorianDate, HebrewDate, to_hebrew, to_gregorian, weekday

# What Hebrew date and weekday corresponds to 31 October 1867?
g = GregorianDate(1867, 10, 31)
h = to_hebrew(g)
print(h)            # HebrewDate(year=5628, month=8, day=2)  -> 2 Marheshvan 5628
print(weekday(g).name)   # THURSDAY

# Convert a Hebrew date back to Gregorian.
print(to_gregorian(HebrewDate(5785, 7, 1)))   # GregorianDate(year=2024, month=10, day=3)

Every calendar reduces a date to an integer Rata Die (RD) day count and rebuilds a date from it, so any two calendars are interconvertible through RD:

from hebrewcal import GregorianDate, to_julian

GregorianDate(2026, 6, 26).to_rd()     # 739793
to_julian(GregorianDate(2026, 6, 26))  # JulianDate(year=2026, month=6, day=13)

Features

• Proleptic Gregorian and Julian calendars, with an explicit, configurable Julian/Gregorian reform helper.
• A complete Hebrew calendar: molad and halakim, the dechiyot ("four gates"), year typing (deficient / regular / complete), the keviah signature, and the Metonic cycle.
• Bidirectional conversion between any supported calendars through Rata Die.
• Parsing of Gregorian input (ISO 8601, DIN 5008 and slash form) and formatting in numeric and named styles.
• A gematria converter between integers and Hebrew numerals.
• Month and weekday name tables (transliteration, Babylonian, biblical).
• The Anno Mundi era with a documented "missing years" notice.

Documentation

Full documentation, including a user guide with many examples, lives at hebrewcal.readthedocs.io.

Development

git clone https://github.com/bsesic/hebrewcal.git
cd hebrewcal
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pre-commit install

Run the lint gate and the test suite:

flake8
ruff check .
mypy
pytest

See CONTRIBUTING.md for the branching strategy and conventions.

Citation

If you use hebrewcal in academic work, please cite it. Citation metadata is provided in CITATION.cff, and each release is archived on Zenodo with a DOI (see the release page for the version-specific DOI).

License

MIT © Benjamin Schnabel