trud-calendar-core

Headless calendar engine — types, state, date utils, layout algorithms, recurrence. Zero dependencies.

This is the framework-agnostic core of trud-calendar. Use it to build calendar UIs in any framework — React, Vue, Svelte, Angular, or vanilla JS.

Installation

npm install trud-calendar-core

What's included

• Types — CalendarEvent, CalendarView, DateString, PositionedEvent, EventSegment, RecurrenceRule, UndoStack, VirtualRange
• Date utils — addDays, startOfWeek, startOfMonth, isSameDay, eachDayOfRange, getVisibleRange, ...
• Formatting — formatToolbarTitle, formatTime, formatTimeRange, formatAgendaDate (all via Intl)
• Event utils — sortEvents, filterEventsInRange, segmentMultiDayEvent, computeTimePositions, groupEventsByDate
• Recurrence — expandRecurringEvents, generateOccurrences (RFC 5545 RRULE)
• Undo/Redo — createUndoStack, pushState, undo, redo (generic, framework-agnostic)
• Virtualization — filterVisibleEvents, scrollToViewportRange
• Layout — buildOverlapGroups, assignColumns, computeTimePositions (column-packing)
• State — calendarReducer, createInitialState

Quick example

import {
  getVisibleRange,
  filterEventsInRange,
  computeTimePositions,
  formatTime,
} from "trud-calendar-core";

const range = getVisibleRange("2026-03-13", "week", 1);
const visible = filterEventsInRange(events, range.start, range.end);
const positioned = computeTimePositions(timedEvents, 8, 20);

for (const { event, top, height, column, totalColumns } of positioned) {
  console.log(`${formatTime(event.start, "en-US")} ${event.title}`);
}

All dates use ISO 8601 strings — no Date objects.

Documentation

Full docs at github.com/trudapp/trud-calendar

License

MIT