calendaryjs-plugin-liturgical

New to calendaryjs? Start with the core README — this plugin builds on its engine.

Adds the Roman Catholic liturgical calendar to calendaryjs: Easter (via the Computus algorithm) plus the movable feasts declared as offsets from it, so the whole cycle follows automatically each year.

Install

npm i calendaryjs calendaryjs-plugin-liturgical

Use it

Register the plugin, then declare easter and offset events — an offset is placed relative to Easter (negative = before, positive = after):

import { calendary } from "calendaryjs";
import { liturgical } from "calendaryjs-plugin-liturgical";

const cal = calendary().use(liturgical());

cal.addGroup({
  id: "church",
  events: [
    { type: "easter", id: "easter", title: "Easter Sunday" },
    {
      type: "offset",
      id: "ash-wednesday",
      baseEvent: "easter",
      offsetDays: -46,
      title: "Ash Wednesday",
    },
    {
      type: "offset",
      id: "palm-sunday",
      baseEvent: "easter",
      offsetDays: -7,
      title: "Palm Sunday",
    },
    { type: "offset", id: "pentecost", baseEvent: "easter", offsetDays: 49, title: "Pentecost" },
  ],
});

cal.getEventsInRange("2025-01-01", "2025-12-31");

Common feasts ship as ready-made presets:

import { EASTER, ASH_WEDNESDAY, PALM_SUNDAY, PENTECOST } from "calendaryjs-plugin-liturgical";

cal.addGroup({ id: "church", events: [EASTER, ASH_WEDNESDAY, PALM_SUNDAY, PENTECOST] });

Compute Easter directly

import { computeEaster, easterRelativeDate } from "calendaryjs-plugin-liturgical";

computeEaster(2025); // → Date — Easter Sunday 2025
easterRelativeDate(2025, 49); // → Date — Pentecost (Easter + 49)

Reference

Event types — easter · offset (baseEvent + offsetDays), plus every standard event property.

Exports — liturgical() · presets (EASTER, PENTECOST, GOOD_FRIDAY…) · computeEaster · easterRelativeDate · daily-calendar utils (getLiturgicalDay, getSeason…).

License

MIT. This plugin requires the calendaryjs core, which is licensed PolyForm Noncommercial — so commercial use of the combined work requires a commercial license for the core. See Commercial licensing.