npm i @romcal/calendar.mexico


JavaScript library that generates liturgical calendars of the Roman Rite of the Roman Catholic Church.

by romcal

3.0.0-alpha.0 (see all)License:MITTypeScript:Built-In
npm i @romcal/calendar.mexico


Generates liturgical calendars of the Roman Rite of the Roman Catholic Church.

Supports Node v14+, Modern Browsers (desktop and mobile).

License Downloads

latest beta dev


Quick start (below on this page)

Main usages



Romcal generates liturgical calendars of the Roman Rite of the Roman Catholic Church. Output conforms to the revised liturgical calendar as approved by Paul VI in Mysterii Paschalis dated 14 February 1969. The rules are defined in the General Instruction on the Roman Missal (GIRM), the General Norms for the Liturgical Year and the Calendar (GNLY), and the General Instructions of the Liturgy of the Hours (GILH).

  • 📅 Perpetual calendar:
    romcal allows querying liturgical dates for any year in the standard calendar. Note that dates for years before 1969 will still be returned in a format conforming to the calendar reforms of 1969, even though those years came before this calendar reform.

  • ⚙️ Configure and refine output:
    output can be configured for the civil calendar year, i.e. the Gregorian year (Jan 1 to Dec 31) or the liturgical year (First Sunday of Advent to Christ the King). You can filter queries to allow more streamlined date results to be obtained for the year. Additional output options are described below in the usage section.

  • 🌐 i18n, localization and calendars:
    romcal aims to have your liturgical calendars and contents in your native language, and support various liturgical calendars (national, diocesan...). You are more than welcome to contribute, add new localization, and improve the quality of this library!

Getting started


Romcal can be added to your project using npm or yarn:

# npm
npm install romcal@dev

# yarn
yarn add romcal@dev

The default export is CommonJS compatible (cjs).

In the /dist folder you may find additional builds for es6 modules (esm) or to be used globally from the browser (iife). The correct entry points are already configured in the package.json so there should be no extra setup to get the best build option.

Calendars installation

The romcal library only include the General Roman Calendar (GRC), and the Proper of Time. By default, there is no other calendars, neither translation (even in English) nor extra martyrology metadata.

The complete GRC, and any other particular calendar (for a country, a region or a diocese) are available as separated plugins, that contain a bundle of the calendar data, localizations, and a martyrology catalog (containing extra metadata).

For example, to install the General Roman Calendar and the calendar of France:

# npm
npm install @romcal/calendar.general-roman@dev
npm install @romcal/calendar.france@dev

# yarn
yarn add @romcal/calendar.general-roman@dev
yarn add @romcal/calendar.france@dev

The complete list of localized calendar is available here.

Load from CDN

You can also directly add a script tag loading romcal from one of the CDNs providing it:


esm or cjs:

Make sure to use a fixed version in production like https://unpkg.com/romcal@3.0.0-dev.29/dist/cjs/romcal.js as passing no version will redirect to the latest version which might contain breaking changes in the future.



Basic samples

Initialize a Romcal object

Before generating any kind of data, you must first generate a new Romcal() object.

1. Import Romcal

// as esm
import Romcal from 'romcal';
import { France_Fr } from '@romcal/calendar.france';
// or as cjs
const Romcal = require('romcal');
const { France_Fr } = require('@romcal/calendar.france');
<!-- or as iife in a web HTML page -->
<script src="https://unpkg.com/romcal@3.0.0-dev.29/dist/iife/romcal.js"></script>
<script src="https://unpkg.com/@romcal/calendar.france@3.0.0-dev.29/iife/fr.js"></script>

2. Initialize Romcal

With default options:

const romcal = new Romcal();

Or with any of the optional options:

// Initialize romcal (all options are optional)
const romcal = new Romcal({
  localizedCalendar: France_Fr, // The localized calendar to use with romcal
  scope: 'gregorian' | 'liturgical', // Default: 'gregorian' (Jan 1 to Dec 31). Optionally: 'liturgical' (the first Sunday of Advent to the last Saturday of Ordinary Time)
  epiphanyOnSunday: true | false, // Epiphany always a Sunday (between January 2 - 8), or on January 6
  corpusChristiOnSunday: true | false, // Corpus Christi always a Sunday, or the Thursday after Trinity Sunday
  ascensionOnSunday: true | false, // Ascension always a Sunday, or the 40th day of Easter (a Thursday)

For further information about romcal configuration and the default options: 📚 Configuration options.

You can also take a look to the ./examples directory, which contain additional examples:

  • html-web-page – loading romcal in a HTML script tag (iife).
  • react-app – a basic React application loading and displaying romcal data.
  • rest-api-with-express – a REST API using Node.js and Express, written as CommonJs (cjs).
  • rest-api-with-fastify – a REST API using Node.js and Fastify, written as ES Module (esm).

Generate a calendar .generateCalendar(year)

The year parameter is optional.

Below, 2 examples to generate a calendar for a specific year or the current year.

// Get a romcal calendar for 2030, using a Promise:
romcal.generateCalendar(2030).then((data1) => {

// Or get a romcal calendar for the current year, using async/await:
const data2 = await romcal.generateCalendar();

This method produces an Object of key/values, where the key is a date (as a ISO8601 string), and the value is an Array of LiturgicalDay objects that can occur on a specific day. The first LiturgicalDay object is the default one, the following objects are optionals (e.g. optional memorials).

  key: 'mary_mother_of_god',
  name: 'Mary, Mother of God',
  date: '2020-01-01',
  precedence: 'GENERAL_SOLEMNITY_3',
  rank: 'SOLEMNITY',
  rankName: 'Solemnity',
  isHolyDayOfObligation: true,
  isOptional: false,
  colors: ['WHITE'],
  seasons: ['CHRISTMASTIDE'],
  seasonNames: ['Christmas'],
  periods: ['CHRISTMAS_OCTAVE'],
  martyrology: [],
  titles: [],
  cycles: {
    sundayCycle: 'YEAR_A',
    weekdayCycle: 'YEAR_2',
    psalterWeek: 'WEEK_2',
  calendar: {
    weekOfSeason: 2,
    dayOfSeason: 8,
    dayOfWeek: 3,
    nthDayOfWeekInMonth: 1,
    startOfSeason: '2021-12-25',
    endOfSeason: '2022-01-09',
    startOfLiturgicalYear: '2021-11-28',
    endOfLiturgicalYear: '2022-11-26',
  fromCalendar: 'proper_of_time',
  fromExtendedCalendars: [],

By default, the range dates correspond to a Gregorian calendar (Jan 1 to Dec 31). Except if you previously initialized the Romcal object with { scope: 'liturgical' }: the range corresponds to a liturgical year (the first Sunday of Advent to the last Saturday of Ordinary Time).

// Will generate a liturgical calendar, from 2029-12-02 to 2030-11-30
const romcal = new Romcal({ scope: 'liturgical' });
const data = await romcal.generateCalendar(2030);

For further information: 📚 Output data and JSON schema.

Get one liturgical day .getOneLiturgicalDay(key, options)

Instead of returning LitugicalDay objects for the whole year, you can try to retrieve only one object by its key.

const data = romcal.getOneLiturgicalDay('easter_sunday');

It will return:

  • The corresponding LiturgicalDay found in the calendar.
  • Or null if the LiturgicalDay exists in the calendar definitions, but do not occur in this specific year.
  • Or undefined if the desired LiturgicalYear do not exist in the calendar.

By default, romcal compute this LiturgicalDay in the context of the current year. You can set a specific year in the options: { year: 2030 }.

⚠️ Important: from this method, romcal do not compute the whole year for performance reasons. Some metadata (especially the seasons and the periods in Christmas Time, and the precedence rules) might be incomplete or not accurate.

If this is an issue for your requirements, you can tell Romcal to compute first the whole year to ensure data integrity, by setting this option: { computeInWholeYear: true }.

const data = romcal.getOneLiturgicalDay('ordinary_time_12_sunday', {
  year: 2022,
  computeInWholeYear: true,
// Will return `null`, because `corpus_christi` is taking precedence over `ordinary_time_12_sunday` in 2022

Get all liturgical day definitions .getAllDefinitions()

The 2 methods above (.generateCalendar and .getOneLiturgicalDay) are returning LiturgicalDay objects, in the context of a year. That is, every LiturgicalDay objects have a date property, and are sorted and possibly removed depending on the year context and seasons/precedence rules.

However, you might need to retrieve all possible calendar definitions, without any rules or year context.

The .getAllDefinitions() method returns absolutely all LiturgicalDayDef objects that are part of a liturgical calendar. The returned object is a key/value, where the key is the key of the LiturgicalDayDef object, and the value is the LiturgicalDayDef itself.

const definitions = romcal.getAllDefinitions();

Note that a LiturgicalDayDef object is different from a LiturgicalDay object. The first one contain already most of the metadata, but do not have the date property, and the seasons & periods might be incomplete. Also, some properties like colors, ranks, precedence might be updated in a LiturgicalDay object, according to the year context and seasons/rules.

Get the date of major celebrations .date(year).fn()

You might only need the Date of a liturgical day, without computing all other metadata or a whole calendar.

This gives you access to all methods from the Dates class: ./lib/utils/dates.ts.

The year parameter is optional (taking the current year by default, if not provided).

const romcal = new Romcal();
const dates = romcal.dates(2030);
const easterOf2030 = dates.easterSunday();

All these methods will return a Date object (or a range of Date objects).

Note that you can also pass a year property to the last method:

const pentecostOf2030 = romcal.dates().pentecostSunday(2030);


Romcal is an open source project, this means you are more than welcome to contribute! Especially to find bugs or write new tests, verify or complete calendars, or pull new localization.

To jump into romcal’s codebase more easily, you might be interested in reading:

Changelog & Release History

See the changelog for the latest updates and important/breaking changes.

Module Robustness & Data Integrity

Romcal’s code logic aim to be fully compliant with the General Instruction on the Roman Missal (GIRM) and the General Norms for the Liturgical Year and the Calendar.

Calendar entries are pulled from the missal and official sources for the General Roman Calendar. Other calendar entries are pulled from various liturgical books and sources from the internet (when we don't have access to the missal or proper official books of the country / region). As such the accuracy of all calendars might not be ensured. If you find an incorrect calendar entry (e.g. wrong date, wrong feast rank, spelling issue, typos), you are most welcome to contribute or inform the team on the GitHub issue tracker, so that the necessary changes can be made to make this a more robust and reliable module.


This node module is inspired by the C program romcal written by Kenneth G. Bath. This module, while exhibiting similar output, is written ground up using different tools and technologies and exposes many new functionalities.

Additional credits for bug fixes, localization and suggestions can be seen at here.




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