# Optional Google Calendar integration boundary

The app now uses the real **Asia/Tokyo** date for its Today page and can export an `.ics` snapshot for Apple Calendar or Google Calendar. Supabase remains the live shared source inside the app.

A true two-way Google Calendar integration is deliberately not enabled by default. It requires a Google Cloud project, Calendar API enablement, an OAuth consent screen, browser OAuth credentials, explicit user authorization, incremental-sync token storage, token refresh handling, event ownership rules, conflict handling, and a privacy review before hosting.

## Beginner-safe current workflow
1. Open **Calendar Sync** in the hosted app.
2. Download `japan-honeymoon-trip-calendar.ics`.
3. Import it into Apple Calendar or Google Calendar as a travel snapshot.
4. Keep itinerary edits in the app. Supabase sync is the live source for both phones.
5. Export a new snapshot only after a meaningful itinerary revision.

## Later production upgrade
Implement a server-side Google Calendar adapter only after Cloudflare hosting and Supabase sync are stable. Use OAuth rather than embedding secrets in the browser. Preserve a mapping between app day IDs and Google Calendar event IDs, and use Google incremental synchronization tokens for subsequent updates.