Show HN: calsdk, one TypeScript API for Google Calendar, Outlook and iCloud

Every calendar. One API. Events, free time and sync for nine providers, including Google Calendar, Outlook and iCloud, in one typed TypeScript API. Website · Docs · Quickstart · Playground · FAQ The website opens with a live demo. It runs in your browser on six sample calendars, using the real listEvents, findFreeTime and createEvent. To edit code without installing anything, open the playground on StackBlitz. Or install it: npm i @cal-sdk/core @cal-sdk/mock @cal-sdk/mock keeps a calendar in memory, so you can try everything without an account or a network: import { createEvent, findFreeTime, listEvents } from '@cal-sdk/core'; import { mockCalendar } from '@cal-sdk/mock'; const calendar = mockCalendar(); await createEvent({ calendar, event: { title: 'Standup', start: { dateTime: '2026-11-09T09:30:00', timeZone: 'Europe/Berlin' }, end: { dateTime: '2026-11-09T09:45:00', timeZone: 'Europe/Berlin' }, recurrence: ['RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR'], }, }); const { events } = await listEvents({ calendar, timeMin: '2026-11-09T00:00:00+01:00', timeMax: '2026-11-14T00:00:00+01:00', }); const { slots } = await findFreeTime({ calendars: [{ calendar }], timeMin: '2026-11-09T00:00:00+01:00', timeMax: '2026-11-10T00:00:00+01:00', duration: 30, workingHours: { start: '09:00', end: '11:00', timeZone: 'Europe/Berlin' }, }); Switch calendars, not code When the logic works, swap the mock for a real calendar. Only the import and the line that creates calendar change, and events come back in the same shape from every provider. import { google } from '@cal-sdk/google'; const calendar = google({ accessToken: () => getFreshAccessToken() }); Compare providers has the full list of what each one can do. What it handles for you Recurrence is always an RRULE. Outlook stores a pattern object and Zoom numbers its weekdays. You read and write one RRULE, and listing expands a series into occurrences you can move one at a time, or all together. Time zones that survive clock changes. A 9:30 New York standup stays at 9:30 in New York, wherever it's viewed from. Warnings, not silent changes. When a provider can't do exactly what you asked, such as a color outside Google's palette, the call saves what it can and returns a warning. If going ahead would lose data, it throws instead. Free time across providers. findFreeTime finds slots when a Google calendar and an Outlook calendar are both free. Sync. syncEvents returns only what changed since a saved cursor. An expired cursor is its own error, so a full resync is one branch. Errors you can branch on. Conflicts, rate limits, auth failures and missing events each have their own error class. Types that follow the calendar. Provider options are checked against the calendar you pass, so a misspelled option fails to compile. Good to know It's a library, not a hosted service. It runs in your app and calls each provider directly with tokens you pass in. Your users' calendar data doesn't pass through anyone else. It doesn't run OAuth. Pass a token, or a function that returns a fresh one. It runs anywhere with fetch. Node.js 20 or later, Bun, Deno and edge runtimes, with no vendor SDKs. It's tested on the real APIs. Google, Outlook, Zoho, Zoom, Cal.com and Calendly are recorded live and replayed in CI. You can add your own provider. A provider is one object with a few functions, checked by a shared conformance suite. See Build a provider. Working on calsdk This repo uses Bun. bun install bun run build # build the packages bun run test bun run typecheck bun run lint The website and docs live in apps/web. Build the packages first, then run bun run dev in apps/web.