Calendar API for Google Calendar and Outlook

List, create and update events, RSVP and find open slots across your users' Google and Microsoft calendars with one REST API, with a webhook for every change.

Start building free View API docs

Google + Outlook
Availability
Webhooks

Thu, 14 Jan

09:30

Team standupTeams

14:00

Demo with NorthwindGoogle Meet, 3 guests

16:30

1:1 with PriyaRoom 4B

Free for everyone30 min

11:0011:3015:0015:30

calendar.event.createdDemo with Northwind

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Supported platforms

One API. Google Calendar and Outlook

Connect a Google or Microsoft account and call the same calendar endpoints for both

Google Calendar
Gmail
Google Drive
Google Contacts

Google Calendar, two-way

Events with Google Meet links, RSVPs and free slots on Google calendars.

Outlook Calendar
Outlook
OneDrive
Outlook Contacts

Outlook Calendar, two-way

Events with Teams meetings, RSVPs and free slots on Microsoft 365 calendars.

Explore Microsoft

How it works

From signup to first event in three steps

1

Key name

e.g., Production API key

Permission

Read & write

Read only

Profile access

Full access (all profiles)

Create key

Get your API key

Sign up free and create a key in the dashboard.

2

Profile

Default

Google

emailcalendarfilescontacts

Microsoft

emailcalendarfilescontacts

Connect Google or Microsoft

Request a connect link with the areas you need. Each account gets an ID for API calls.

3

POST /v1/calendar/events

curl -X POST "https://zernio.com/api/v1/calendar/events" \
  -H "Authorization: Bearer $ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "accountId": "acc_xxx",
    "title": "Demo with Northwind",
    "start": "2027-01-14T14:00:00+01:00",
    "end": "2027-01-14T14:30:00+01:00",
    "participants": [{ "email": "lena@northwind.io" }],
    "conferencing": "google_meet"
  }'

Book the meeting

POST /v1/calendar/events creates the event, invites the guests and adds a Meet or Teams link.

Features

Everything you need for scheduling

Events

Calendars and eventsEvery calendar the user can see
FiltersDate range, title, location, iCal UID
Create, update, deleteTitle, guests, location, visibility
Recurring eventsRRULE in, instances expanded out
Meeting linksGoogle Meet or Teams on create

Availability

Free/busyBusy blocks for up to 10 accounts
Open slotsFree for everyone or for anyone
Open hoursPer participant, in their own timezone
BuffersPadding before and after meetings
Slot length5 minutes to 8 hours, any interval

Respond and listen

RSVPAccept, decline or tentative, with a note
RemindersCalendar default or up to 5 of your own
TimezonesAny IANA zone, per request
MetadataYour own keys on every event
calendar.event.*Created, updated and deleted

Frequently asked questions

Add Google Calendar and Outlook to your app

Connect a calendar, book the first meeting and get a webhook for every change.

Start for free Read the docs

Google + Outlook
Availability
Webhooks