Google Calendar vs The Calendar

The Google Calendar API reads and writes events, calendars, free/busy data, and reminders for any Google account that's granted OAuth consent, with push-notification channels available so an app can watch a calendar for changes instead of polling it. It's the same REST API that powers Calendar add-ons and third-party scheduling tools like Calendly. Usage is free under Google's shared per-minute and per-project quotas (10,000 requests/minute/project as of the May 2026 quota update); there's no separate paid tier for the API itself, only future overage billing above a 1,000,000-requests-a-day threshold.

The Calendar publishes pre-generated, static JSON (and downloadable .ics) files for US federal and all-50-state holidays (2025–2028), 30 countries' public holidays, plus FOMC meeting dates, US tax deadlines, market holidays, and key-date calendars for a dozen sports leagues. Every one of its 99 documented endpoints is a flat file behind Cloudflare, so there's no authentication, no rate limit, and CORS is wide open — licensed CC BY 4.0 as long as you link back.