Anniversaries & milestones

The 0.6.0 recurrence primitives, all declarative on a const event.

import { calendary } from "calendaryjs";

const cal = calendary();
cal.addGroup({
  id: "milestones",
  events: [
    // Only the 1/5/10/25/50-year anniversaries, counted from the wedding (2010).
    {
      type: "const",
      id: "wedding",
      month: 6,
      day: 20,
      title: "Wedding anniversary",
      origin: 2010,
      keepOrdinals: [1, 5, 10, 25, 50],
    },
    // A Feb-29 birthday, clamped to the last day of February in non-leap years
    // instead of spilling into March 1.
    { type: "const", id: "leapling", month: 2, day: 29, title: "Leap-day birthday", onMissingDay: "clamp" },
  ],
});

cal.getEvents("2015-06-20")[0].ordinal; // → 5   ("N years", no occurrenceYear − origin math)
cal.getEvents("2013-06-20"); // → []   (3 years isn't a kept milestone)
cal.getEvents("2020-06-20")[0].title; // → "Wedding anniversary" (10 years)

cal.getEvents("2025-02-28").map(e => e.title); // → ["Leap-day birthday"] (clamped)
cal.getEvents("2024-02-29").map(e => e.title); // → ["Leap-day birthday"] (real leap day)

• keepOrdinals — emit only the listed anniversaries; origin (defaults to startYear) is the anchor. For the arithmetic “every Nth year” case use interval
  • startYear instead.
• onMissingDay — "overflow" (default, Feb 29 → Mar 1), "clamp" (last valid day), or "skip" (no occurrence that year).
• ordinal — occurrenceYear − (origin ?? startYear) on every computed event.

Full reference: Event types.