Google Calendar
HTTPS CORS ? OAuth
Display, create and modify Google calendar events
API Endpoint
https://developers.google.com/google-apps/calendar/More Calendar APIs
Worldwide Holidays
HTTPS CORS ? apiKey
Industry-leading Holiday API. Over 5,000 holidays and thousands of descriptions. Trusted by the World’s leading companies
HTTPS CORS ? apiKey
Catholic liturgical calendar
HTTP CORS ? Free