Hebrew Calendar

A Java library for Jewish calendar computations — dates, festivals, zmanim, Torah readings and daily learning. Java 11, no runtime dependencies.

Project page and API documentation

It powers hebrewcalendar.net

Every date, zman and reading on hebrewcalendar.net — its calendars, zmanim pages, printable schedules and shul displays — is computed by this library. The mobile app runs the same calendar as a companion C library, checked against this one day by day.

What it does

• Dates — Jewish, Gregorian and Julian calendars, converted in any direction; leap years, month lengths, anniversaries and yahrzeits, including the dates that fall only in some years.
• Festivals and fasts — Yom Tov, chol hamoed, rosh chodesh, fasts and their deferrals, the named Shabbatot, the omer, Chabad dates, and US holidays. Israel and the diaspora each keep their own schedule.
• Zmanim — sunrise and sunset from the NOAA solar calculations, dawn and nightfall in several opinions, candle lighting, chametz deadlines, when a fast begins and ends, and sane answers where the sun does not rise or set.
• Tekufot and the molad — the four solar seasons according to Shmuel or Rav Ada, the molad of any month, when Tal uMatar begins, and Birkat HaChama.
• Torah readings — the weekly parsha with its aliyot, festival and special readings, and haftarot across twenty-six customs, resolved through their fallback tree.
• Daily learning — Chumash, Daf Yomi, Rambam (one chapter and three), Sefer HaMitzvot, Tanya, Tehillim by day of the month and through Elul, Pirkei Avot, and the Sotah sefirah count.

Using it

<dependency>
  <groupId>net.hebrewcalendar</groupId>
  <artifactId>hebrewcalendar</artifactId>
  <version>2.1.0</version>
</dependency>

// A Gregorian date as a Jewish one
IDate<JewishCalendar> today =
    ICalendar.JEWISH.convert(ICalendar.GREGORIAN.fromYMD(2026, 9, 18));

// Zmanim for a place and a day
Location montreal = new Location(45.5017, -73.5673, 0.0, "America/Montreal", false, false);
Zmanim zmanim = new Zmanim(LocalDate.now(), montreal);

ZonedDateTime sunset = zmanim.getSunset().getTime();
Zman candles = zmanim.getCandleLightingZman();   // null unless candles are lit tonight

Building

git clone --recurse-submodules https://github.com/imush/hebrewcalendar.git
cd hebrewcalendar
mvn package

Calendar names and reading schedules come from the shared hebrewcalendar-data repository, included as a submodule and compiled into the jar.

Checked against opentorah

Readings and date conversion are both compared against opentorah, the source of the reading data: every reading situation over eighty years, and every day of two centuries. mvn test runs those comparisons with the rest of the suite.

Releasing

See RELEASING.md.

License

BSD 3-Clause. See LICENSE.