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. Feature-complete against the roadmap: calendar core and conversion, astronomy, holidays, religious times, and alternative calendars are all implemented, documented and tested.

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 (explicit, configurable Julian/Gregorian reform) and a complete Hebrew calendar (molad/halakim, dechiyot, year typing, keviah, Metonic cycle), all interconvertible through Rata Die.
• Parsing (ISO 8601, DIN 5008, slash form), formatting, a gematria converter, month/weekday name tables (transliteration, Babylonian, biblical), and the Anno Mundi era with the documented "missing years" notice.
• Astronomy (pure Python): solar position, sunrise/sunset, twilight, the molad as a civil instant.
• Holidays for Israel and the Diaspora: festivals, fasts (with postponement), modern Israeli days, minority feasts, Rosh Chodesh, the Omer and the special Shabbatot.
• Religious times: Shabbat candle lighting and Havdalah, zmanim, the molad announcement, yahrzeit, Torah readings, and the Shmita cycle.
• Alternative calendars: the Qumran 364-day calendar, plus documented computed Samaritan and Karaite models.
• An optional command-line interface (see below).

Command line

Installing the package provides a hebrewcal command (and python -m hebrewcal):

$ hebrewcal convert 1867-10-31
2 Marheshvan 5628 (Yom Chamishi)

$ hebrewcal shabbat 2026-06-26 --lat 40.71 --lon -74.01 --tz America/New_York
Candle lighting: 20:13
Havdalah: 21:21

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.

• Concept DOI (always resolves to the latest version): 10.5281/zenodo.20583972
• Each release also has its own version-specific DOI on the Zenodo record.

License

MIT © Benjamin Schnabel