Your calendars.
Your data.
Tandem connects the calendars you choose. Here is what this deployment uses, stores, and shares to make that happen.
Signing in
Sign in with Apple creates your Tandem account. The app stores your account identifier, the name and email Apple shares, and session records. Better Auth uses a session cookie to keep you signed in. Apple sign-in does not grant access to your calendar.
Connecting your calendars
For iCloud, Tandem uses your Apple account email and an app-specific password. For Google, it uses the OAuth access and refresh tokens issued after you authorize Calendar access. These provider credentials are encrypted before storage in Cloudflare D1 using a separate Worker secret.
The application can decrypt these credentials when it needs to contact a provider. Encryption at rest does not hide calendar data from the deployment operator.
What gets stored
The database stores connected account identifiers, calendar names and IDs, selected calendar pairs, event mappings and snapshots used to detect changes, sync state, and recent activity. Event snapshots can contain titles, notes, locations, dates, times, and recurrence details.
Provider credentials are encrypted. Event snapshots, account metadata, and activity are stored in the deployment’s database and are not separately encrypted by the application. Cloudflare also processes request and operational data as the hosting provider.
What gets shared
When you start syncing a pair, Tandem sends supported event details from each selected calendar to the other provider. Existing events are merged on the first sync. Later edits and deletions propagate in both directions.
Your selected calendars may be shared with other people inside Apple or Google. Synced event details inherit the destination calendar’s sharing settings. Check those settings before linking a personal calendar to a work or shared calendar.
Tandem includes no advertising or marketing analytics, and does not sell calendar data.
Pausing and removing access
Pause a calendar pair to stop its sync. Remove your calendar pairs before disconnecting an account; disconnecting deletes the stored provider credentials. Removing a pair or disconnecting leaves events already copied to Apple and Google in place.
You can also revoke the app-specific password in your Apple account or remove Tandem’s access in your Google account. Revoking access prevents further provider requests but does not delete the app’s existing records.
For complete removal of your Tandem account, activity, and any remaining stored data, contact the person who operates this deployment. The app currently does not provide a self-service account deletion screen. Copies in provider calendars and Cloudflare backups follow those services’ separate retention policies.
Sync limitations
Tandem syncs supported calendar event data, not every feature of either provider. Attendees and invitations are not synced. Some recurring-event exceptions are skipped with a visible error. Read the sync behavior guide before connecting calendars.