10+ Best Calendar APIs to Streamline Your Scheduling Process [2023]

Discover the best calendar APIs for 2023. Learn the best free and paid APIs to help you integrate calendar functions into your applications quickly and easily.

10+ Best Calendar APIs to Streamline Your Scheduling Process

Calendar APIs allow businesses to integrate applications with calendars across service providers, such as Microsoft Outlook and Google Calendar. Without calendar APIs, manually building scheduling connectivities within an app or website exhausts resources and time. 

Using calendar APIs means development teams can focus on building mission-critical features that maximize adoption and retention. Businesses can save time while increasing scheduling productivity for their end users and easily capture valuable insights. 

But determining which calendar API will best optimize your scheduling workflows can be difficult. So today, we’ll cover the best calendar APIs on the market so you can find the right one for your business. 

What is a calendar API?

A calendar API allows developers to integrate calendar functionality into their applications and websites. With the help of calendar APIs, developers can easily centralize scheduling workflows within a platform, enabling users to create and manage calendar events, invite attendees, sync calendars, set reminders, and more. 

However, not all calendar APIs are created equal. Well-designed calendar solutions for embedding scheduling capabilities in an application or website should offer a wide range of customization options to fit unique business needs.

But many calendar APIs are missing crucial capabilities that can roadblock your integration efforts. For example, while some calendar APIs offer a free/busy resource showing a single user’s availability,  you may not be able to compare the availability of multiple individuals easily. 

Similarly,  if you want to find availability for multiple meetings with several participants, without the right calendar solution, this functionality can require additional development effort and custom code. 

To avoid spending invaluable developer time and resources, you’ll want to opt for a calendar API that offers availability endpoints. Doing so will allow users to see shared availability across multiple parties, both internal and external, to an organization. And consecutive availability endpoints provide time slots across participants for multiple, consecutive meetings. 

Availability is just one example of features you may be looking for out of a calendar API. When looking for the best calendar solution, it’s important to consider the needs of your users.  

Below we’ve outlined the top calendar APIs on the market, highlighting how they work, key features, and pricing structures to help you determine the best fit for your organization. 

Best calendar APIs

  1. Nylas Calendar API 
Nylas Logo

How it works: The Nylas Calendar API is the best solution for developers to connect their applications to all major calendar providers using a single point of integration. It provides developers the flexibility to quickly and securely build integrations and customize workflows for your users, offering an end-to-end scheduling solution. By helping users automate their scheduling workflows, the Nylas Calendar API creates a seamless user experience in your app which can increase retention and CSAT.  

The Nylas platform goes beyond calendar connectivity and scheduling with a powerful suite of communications integration solutions, including email and contacts APIs.

Key features:

  • Availability endpoints: Remove the back-and-forth with automated scheduling based on free/busy availability  
  • Customizable workflows: Configure scheduling workflows with custom integrations and build native experiences
  • Eliminates siloed data: Capture calendar data in applications and unlock valuable insights to build automated user workflows
  • Automated reminders: Send alerts and notifications for upcoming events across email, Slack, and Microsoft Teams
  • Virtual calendars: Schedule events for people and objects or resources that aren’t associated with an existing calendar account
  • Service accounts: Utilize service accounts for companies that need instant onboarding within organizations
  • Customizable scheduling UI: Tailor scheduling tools with a design unique to your business


Nylas offers a full-service API platform, including an email API, calendar API with a front-end scheduler, and contacts API. Pricing plans vary by the number of connected accounts (end users).

Talk to an expert today to choose the best plan for your business. 

  1. Cronofy Calendar API 

How it works: Cronofy’s calendar API allows developers to connect their applications with multiple calendar service providers, such as Google Calendar and Apple Calendar. The API provides developers with guides and SDKs to assist them in navigating the platform. One of the key features of the Cronofy Calendar API is its real-time availability, which helps users avoid scheduling conflicts. 

The API also includes UI elements that can be embedded into an application and the ability to send out calendar invites with video conferencing details. 


Key features:

  • Enables users to build scheduling features into calendars
  • Enables users to build real-time, two-way sync across calendars
  • Full create, read, update, delete (CRUD) operations that allow Cronofy to read and delete individual events, on behalf of the user, created by the API 


Cronofy offers annual and monthly pricing packages for their API and scheduler separately. 

  • Cronofy API (Annual plan) 
    • Starter: $119 per month
    • Emerging: $729 per month
    • Growth: $1999 per month
  • Cronofy API (Monthly plan) 
    • Starter: $139 per month
    • Emerging: $819 per month
    • Growth: $2,399 per month
    • Strategic: Customizable plan. Contact Cronofy for a quote.
  • Scheduler (Annual plan) 
    • Business: $599 per month
    • Enterprise: $1,899 per month
  • Scheduler (Monthly plan)
    • PAYG: $15 per month
    • Business: $699 per month
    • Enterprise: $2,299 per month
  1. Calendly API 

How it works: Calendly enables users to automate appointment and meeting scheduling. It offers a REST-based API that allows businesses to retrieve Calendly links, report on scheduled meetings, and retrieve availability for a specific event type for team members within an organization. The platform also has an Embed API, which lets businesses add a user’s Calendly scheduling page to their websites by enabling inline, pop-up text, or pop-up widget variations. 

Calendly’s API is read-only, intended to make it easier for businesses to embed calendar functionality on web pages. For example, it can only read the free/busy status of events in users’ calendars. For organizations looking to extract scheduling data, you’ll want to consider an API that uses event metadata to drive deeper insights.  

Key features:

  • Automates event scheduling, canceling, and rescheduling via webhooks 
  • Enables users to embed Calendly API via OAuth or personal access tokens
  • Admins can report on events and access information about event types 


Calendly is primarily feature-based and offers four pricing models: 

  • Basic: Free
  • Premium: $8 per user per month (annually) | $10 per user per month (monthly)
  • Pro: $12 per user per month (annually) | or $15 per user per month (monthly)
  • Teams: $16 per user per month (annually) | or $20 per user per month (monthly)
  • Enterprise: Custom quote basis
  1. Google Calendar API 

How it works: The Google Calendar API allows for the creation, reading, updating, and deletion of calendar events, as well as the management of calendar settings and the reading of calendar metadata. The API helps handle single or recurring events, calendar management, user preferences, and access control rules.

Google’s calendar API follows RESTful principles and can be accessed via explicit HTTP calls or through the use of Google Client Libraries. The API uses OAuth 2.0 for authentication and supports multiple programming languages.


Key features:

  • Enables users to add events, including recurring events
  • Users can specify and manage a working location where others can view before invitation to an event
  • Push notifications to inform users of changes 
  • Provides extended properties which enables users to store data without an external database 


As a support tool, Google Calendar is free to use. However, it doesn’t have as many features or capabilities as other paid options, like Nylas.

  1. Zoho Calendar API 

How it works: Zoho Calendar is a calendar and scheduling platform that is part of the Zoho suite of productivity and collaboration tools. The platform brings all calendars to one place and enables organizations to collaborate and manage events, appointments, and bookings. The Zoho Calendar API enables developers to customize features in the Zoho Calendar, and integrate the calendar with your application.


Key features:

  • Developers can edit, delete and add an existing calendar 
  • Users to share calendar details and get details of file attached to a created event
  • Enables users to update and move an event from one calendar to another 


While Zoho Calendar is free, pricing for the Zoho Calendar API is not listed online. 

  1. AddEvent API 

How it works: AddEvent is a platform that enables developers to add events to users’ calendars, collect information from attendees during registration, share multiple events through a subscribable calendar, and embed a calendar on a website. 

AddEvent offers both a calendar API and an event API. The calendar API makes it easy for end-users to create, save, and delete calendars, view and delete subscribers, create, save, and delete events, and list all events across all calendars. The event APIs also allow users to create, save, and delete events, as well as manage RSVPs, list events, and manage time zones. 


Key features:

  • List, create, view, edit, delete and share an event
  • Setting events according to timezones 
  • List, view, create and save details about an event RSVP and attendees


AddEvent offers four annual pricing plans:

  • Hobby: Free for personal use only 
  • Small business: $19 per month 
  • Professional: $99 per month 
  • Enterprise: Contact AddEvent for pricing 
  1. Cogsworth API

How it works: Cogsworth is a scheduling software that primarily serves the telemedicine industry. Its API allows users to manage staff working hours and calendar availability to prevent overbookings or double bookings. Cogsworth also lets users sync their calendars and directly write bookings into external calendars. The API enables users to create workflows and utilize pre-built logic, such as recurring appointments, team bookings, approvals, and buffers. 


Key features:

  • Create resources such as staff name, staff hierarchy, working hours and more
  • Query time slot availability for requested resources 
  • Add calendar connections


Cogsworth offers two pricing plans billed monthly and annually:

  • Scheduler: Billed $29/mo annually, or $35/mo monthly
  • Enterprise: Custom pricing 
  1. Timekit API

How it works: Timekit’s API allows developers to create resources, sync calendars, manage projects, and control booking flows. Users can customize their interface and manage bookings through their booking.js kit, which contains various blueprints. The Timekit API also utilizes webhooks for their booking process, which provides users with a real-time view of changes that happen to a booking. 

Key features:

  • Allows users add customizations to timekit calendar or other external calendars 
  • Provides booking infrastructure for businesses 
  • Provides webhooks for data integration 
  • Allows users to create resources and confirm resource availability


Timekit offers four pricing levels: 

  • Essential: $49/mo
  • Professional: $149/mo
  • Platform: $349/mo
  • Enterprise: Contact Timekit for more information
  1. Cal.com API

How it works: The Cal.com API provides access to data models that allow developers to build calendar features into their own applications, including availability displays and specific event mapping. The API allows users to manage teams on self-hosted platforms.


Key features:

  • CRUD bookings and events types
  • Developers can manage user endpoints on self-host enterprises
  • Track the charges required to book some events
  • Members can map users to a particular team role


Cal.com offers three yearly pricing levels: 

  • Free: $0.00/mo/user, ideal for individual consumers
  • Teams: $12/mo/user 
  • Ultimate: $2,370/mo for 30 users
  • Platform: $0.05/booking. Minimum of $189/month
  1. Outlook Calendar API 

How it works: The Microsoft Outlook Calendar API is a solution that caters to personal, educational, and business services. It’s linked with Outlook email services and helps users integrate and manage calendar events and appointments. 

The Outlook Calendar API is synced with other Microsoft 365 products and enables access to phone and email contacts, as well as OneDrive. 


Key features:

  • Create, manage and respond to events 
  • Track changes to an event and decline or accept a meeting 
  • Share a calendar and delegate a calendar to another user 
  • Book meetings at convenient times by enabling free/busy availability check 
  • Schedule recurring events


Microsoft Outlook calendar API is free for personal use but offers a subscription-based model for the business and education sectors.

Summary of top calendar APIs

Are you looking to further narrow down your options? We’ve categorized the top calendar APIs by integrations below. 

Calendar APIs that connect with Google calendars

  1. Nylas 
  2. Calendly 
  3. Cogsworth 
  4. Addevent
  5. Timekit
  6. Zoho
  7. Cronofy

Calendar APIs that connect with Apple calendars

  1. Nylas 
  2. Calendly 
  3. Cronofy
  4. Zoho Calendar
  5. Addevent
  6. Zoho

Calendar APIs that connect with Microsoft Outlook calendars

  1. Nylas
  2. Timekit
  3. Calendly
  4. Cogsworth
  5. Addevent
  6. Zoho
  7. Cronofy

Use the best calendar API

The best calendar API is going to depend on what your business is looking for. If you need to quickly add scheduling and other calendar capabilities to your business application – while saving your developers thousands of hours of building time – Nylas is the top choice. 

Try out the Nylas Calendar API today and revolutionize how you get things done.


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