Calendar APIs let you add calendar capabilities without building from scratch. Every entry below is profiled with trust signals — pricing model, authentication requirements, CORS support, rate limits, and live uptime checks — so you can compare options and pick production-safe choices instead of guessing from a link list.
| API | Pricing | Auth | CORS | Health | |
|---|---|---|---|---|---|
| Abstract Public Holidays Data on national, regional, and religious holidays via API | Freemium | API Key | No | Profile | |
| Calendarific Worldwide Holidays | Freemium | API Key | No | Profile | |
| Calendly API Calendly API for scheduling links, event types, scheduled events, invitees, and webhook subscriptions to automate meeting workflows. | Freemium | OAuth | No | Profile | |
| Checkiday - National Holiday API Industry-leading holiday data with over 5,000 holidays and thousands of descriptions | Freemium | API Key | Unknown | Profile | |
| Church Calendar Catholic liturgical calendar | Free | No | Unknown | Profile | |
| Czech Namedays Calendar Lookup for a name and returns nameday date | Free | No | No | Profile | |
| DigiDates Various date and time calculations | Free | No | No | Profile | |
| Generate iCAL Generates iCal calendar events that can be used across calendar applications | Freemium | API Key | No | Profile | |
| Google Calendar Display, create and modify Google calendar events | Free | OAuth | No | Profile | |
| Google Calendar API Official Google Google Calendar API REST API (v3) discovered via Google APIs Discovery Service. | Unknown | Unknown | Yes | Profile | |
| Google Cloud Tasks API Official Google Cloud Tasks API REST API (v2beta2) discovered via Google APIs Discovery Service. | Unknown | Unknown | Yes | Profile | |
| Google Tasks API Official Google Google Tasks API REST API (v1) discovered via Google APIs Discovery Service. | Unknown | Unknown | Yes | Profile | |
| Hebrew Calendar Convert between Gregorian and Hebrew, fetch Shabbat and Holiday times, etc | Free | No | No | Profile | |
| Holidays Historical data regarding holidays | Freemium | API Key | No | Profile | |
| LectServe Protestant liturgical calendar | Free | No | Yes | Profile | |
| Nager.Date Public holidays for more than 90 countries | Free | No | No | Profile | |
| Namedays Calendar Provides namedays for multiple countries | Free | No | No | Profile | |
| Non-Working Days Simple REST API for checking working, non-working or short days for Russia, CIS, USA and other | Free | No | No | Profile | |
| Non-Working Days Database of ICS files for non working days | Free | No | No | Profile | |
| OpenHolidays API Public and school holidays for many countries via an open REST API | Free | No | No | Profile | |
| Russian Calendar Check if a date is a Russian holiday or not | Free | No | No | Profile | |
| The Calendar API Public holidays for US states and 30 countries plus sports and finance calendars as static JSON | Unknown | Unknown | Yes | Profile | |
| UK Bank Holidays Bank holidays in England and Wales, Scotland and Northern Ireland | Free | No | Yes | Profile | |
| World Time API A simple API to get the current time based on a request with a timezone. | Unknown | Unknown | Yes | Profile | |
| caldays API Public holidays for 195+ countries | Free | API Key | Yes | Profile |
Start with pricing and auth: free tiers and no-auth APIs are fastest to prototype with. Then check CORS if your app calls the API from the browser, and health before you commit — a great API that's been down for a week will block your launch. Each profile below shows all of these signals plus rate limits where documented.