@hebcal/core

Hebcal is a perpetual Jewish Calendar. This library converts between Hebrew and Gregorian dates, and generates lists of Jewish holidays for any year (past, present or future). Shabbat and holiday candle lighting and havdalah times are approximated based on location. Torah readings (Parashat HaShavua), Daf Yomi, and counting of the Omer can also be specified. Hebcal also includes algorithms to calculate yahrzeits, birthdays and anniversaries.

Hebcal was created in 1994 by Danny Sadinoff as a Unix/Linux program written in C, inspired by similar functionality written in Emacs Lisp. The initial JavaScript port was released in 2014 by Eyal Schachter (age 15). This ECMAScript 2015 implementation was released in 2020 by Michael J. Radwin. @hebcal/core targets both browser-based JavaScript and server-side Node.js.

Many users of this library will utilize the HebrewCalendar and HDate interfaces.

Installation

npm install @hebcal/core

Usage

This package exports 3 categories of output:

• dist/bundle.min.js: This includes all dependencies in a single JS file. It's quite large (174KB minified), and should only be used if you aren't using a bundler.
• dist/index.cjs: This includes all of this package's code in a single bundle.
• dist/es/: This directory contains ES modules for each source file in the package. If you're using Rollup, Vite, or another bundler, you should import from here to reduce output sizes.

  • These files do not include polyfills; if you want to support older browsers, use

  • To make tree-shaking work better, import from the most specific file possible; avoid importing from index or hebcal. Some APIs may still need to be moved to specific files. For example:

    import {getHolidaysOnDate} from '@hebcal/core/dist/es/holidays';
    

  • This can save hundreds of kilobytes by dropping Zmanim dependencies if your code doesn't use them.

  • You will need to include @rollup/plugin-node-resolve in your Rollup config.

Synopsis

import {HebrewCalendar, HDate, Location, Event} from '@hebcal/core';

const options: CalOptions = {
  year: 1981,
  isHebrewYear: false,
  candlelighting: true,
  location: Location.lookup('San Francisco'),
  sedrot: true,
  omer: true,
};
const events = HebrewCalendar.calendar(options);

for (const ev of events) {
  const hd = ev.getDate();
  const date = hd.greg();
  console.log(date.toLocaleDateString(), ev.render('en'), hd.toString());
}

API Documentation