Does BusyCal/BusyContacts work with iCloud Advanced Data Protection?

Yes. BusyCal and BusyContacts work normally with iCloud Advanced Data Protection (ADP) enabled.

Apple's own documentation confirms that iCloud Calendar and iCloud Contacts are not end-to-end encrypted, even with ADP turned on — they continue to use standard CalDAV/CardDAV. BusyCal and BusyContacts connect to these services as usual, so nothing changes.

Reminders do gain end-to-end encryption under ADP, but your trusted devices still decrypt that data locally. BusyCal accesses Reminders through Apple's EventKit framework (the same system APIs other apps use), so iCloud Reminders continue to sync normally.

Notes

• If Reminders appear stale after enabling ADP, open Apple's Reminders app once and let it finish syncing, then press ⌘-R in BusyCal to refresh.
• If you change or reset your Apple Account password, Apple revokes app-specific passwords. You'll need to generate a new one and update it in BusyCal/BusyContacts:
  • BusyCal iCloud setup
  • BusyContacts iCloud setup

No BusyCal or BusyContacts setting changes are required.